Lightning produced by thunderstorms presents a very real danger to Colorado residents. Image courtesy VORTEX2 / NSSL.

Thunderstorms and their associated hazards frequently make appearances in Colorado during the spring and summer months.  Lightning presents one of the damaging – and deadly – aspects of these storms and knowing more about the science behind the phenomena helps us to better protect ourselves.

As part of Lightning and Wildfire Safety Awareness Week, this installment from the National Weather Service gives more information on the science behind these bolts of electricity.

From the National Weather Service:

PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE BOULDER CO
600 AM MDT TUE Jun 20 2017

…UNDERSTANDING THE SCIENCE OF THUNDERSTORMS AND LIGHTNING…

Every thunderstorm produces lightning. Lightning is a giant spark that moves within the cloud…between clouds…or between the cloud and the ground. As lightning passes through the air…it heats the air rapidly to a temperature of about fifty thousand degrees Fahrenheit. This causes a rapid expansion of the air near the lightning channel. This rapid expansion causes a shock wave that we hear as thunder.

Thunderstorms will form if there is enough moisture and instability in the atmosphere. As the sun warms the air near the ground…pockets of warmer air begin to rise and cool. Condensation of water vapor causes cumulus clouds to form. Continued heating can cause these clouds to continue to grow upward into the atmosphere. Towering cumulus clouds may be one of the first indications of a developing thunderstorm. The mature thunderstorm has both an updraft of rising motion and a downdraft of sinking cool air accompanied by rain and sometimes hail.

Thunderstorms grow tens of thousands of feet into the atmosphere. In the cloud…precipitation forms as ice crystals…hail…and rain. Collisions between ice particles cause a charge separation…and positively charged ice crystals are carried by the updraft high in the thunderstorm. The heavier hail gathers a negative charge and falls toward the lower part of the storm. The top of the cloud becomes positively charged and the lower part of the storm becomes negatively charged.

Due to the pool of negative charges in the lower part of the storm…a pool of positive charges will develop along the ground and follow the cloud like a shadow. Farther away from the cloud base…but under the positively charged anvil…a strong negative charge may be induced.

Cloud-to-ground lightning can either be a negatively charged flash or a positively charged flash. The negative flash usually occurs between the negative charges in the lower part of the storm and the positive charges on the ground under and near the cloud base. Positive flashes usually occur between the positively-charged upper levels of the storm and the negatively-charged area surrounding the storm.

In the negative cloud-to-ground flash…an invisible…negatively-charged step leader forms near the cloud base and surges downward toward the ground. As this step leader approaches the ground… streamers of positive charge move upward from trees…buildings…and other objects on the ground. When these streamers meet the step leader…the connection is completed…and the result is lightning. The entire process takes place in fractions of a second.

If you are under a thunderstorm and your hair rises…you are in an area where the positive charges are rising up objects towards the storm. It is a dangerous location…because lightning may be about to strike.

The process for a positive flash is similar except that a positive channel usually originates in the anvil of the storm and surges downward. In this case…streamers of negative charge shoot up to meet the positively-charged channel as it approaches the ground. When a connection is made…a positive flash of lightning occurs.

While both negative and positive flashes of lightning can be deadly…the positive flashes generally are more destructive as they typically deliver more overall electrical charge to the ground…and they remain in contact with the ground surface for a longer period of time as compared to a negative cloud-to-ground flash.

The best advice in order to minimize your risk of becoming a lightning strike victim is to get indoors into a substantial shelter the second you hear thunder…and to remain there for at least 30 minutes after the last rumble of thunder.  In general…when thunder roars…go indoors. An enclosed hard topped automobile is also a safe place to be during thunderstorms.

For additional information about lightning or lightning safety…visit NOAA’s Lightning Safety Awareness web site at (in lower case):

http://www.lightningsafety.noaa.gov

Lightning Safety and Wildfire Awareness Series:

• Lightning Safety and Wildfire Awareness Week Introduction
• Lightning and wildfire safety overview
• The science of thunderstorms and lightning
• Outdoor lightning safety – When thunder roars, go indoors
• Indoor lightning safety – Staying safe in your home or office
• When lightning strikes – Rendering aid and the lasting effects of a strike
• Lightning and wildfires – Hand in hand hazards

Lightning is a very real and deadly hazard in Colorado.

Colorado has the rather unenviable distinction of ranking second in the United States for lightning-related fatalities.  During the spring and summer the nice weather finds many residents outside and while clear skies are the norm, storms oftentimes loom and present a very real hazard to residents.

From the National Weather Service:

PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE PUEBLO CO
600 AM MDT MON JUN 19 2017

Colorado Lightning Safety Awareness Week continues through Saturday. Today we discuss the lightning threat across the Centennial State.

In the United States, there are an estimated 25 million cloud-to-ground lightning flashes per year, and each one is a potential threat to both life and property. During the past thirty years, 48 people have been killed each year by lightning on average, while during the last ten years this number is 30. Last year, 38 people were killed by lightning, while many others were injured. All of the people who were killed by lightning in 2016 were involved in outdoor activities.

In Colorado last year, lightning killed 2 people and injured 7. During the past thirty six years, on average, Colorado has had 3 lightning fatalities and 13 injuries per year.

Since 1980, El Paso County, including the Colorado Springs metro area, has had the dubious distinction of having the most lightning casualties, with 10 fatalities and 84 injuries. Larimer County has had 10 fatalities and 75 injuries, while Jefferson County has had 9 fatalities and 38 injuries.

Because it usually affects one or two victims at a time, and does not cause the destruction left in the wake of tornadoes or hurricanes, lightning generally receives less attention.

Many people do not act in a timely manner to protect their lives, and the lives of others, simply because they do not understand all the dangers associated with thunderstorms and lightning.

You need to become aware of the situations that put you at a greater risk of being struck by lightning, and what you can do to reduce that risk. While nearly all people take some protective actions when rain, hail and wind are occurring with thunderstorms, many leave themselves vulnerable to being struck by lightning as thunderstorms approach, move overhead and move away.

Lightning can strike more than 10 miles from the rain area of a thunderstorm. That distance is about as far as you can hear thunder. If you can hear thunder, you could be in danger of being struck by lightning. When Thunder Roars, Go Indoors!

Most lightning deaths and injuries in Colorado occur during the afternoon when lightning is most likely to develop, and when people are more likely to be outside. Quite a few lightning fatalities occur when little or no rain is falling.

The chance that you will be struck by lightning in the United States is about 1 in 960 thousand for each year of your life. However, your chance of being struck will depend on whether you consistently practice all the lightning safety rules.

Lightning starts around half of the forest and rangeland wildfires across the state. Colorado averages around 2500 wildfires each year. Many of these lightning caused fires occur with very little or no rain. These storms often generate gusty winds, which can fan the flames of the fire.

During this Lightning Safety Awareness Week, the National Weather Service will provide a variety of information on lightning in Colorado.

On Tuesday, the science of lightning will be discussed.

On Wednesday, the topic of the day is outdoor lightning risk reduction. On Thursday, we will have information on indoor lightning safety.

On Friday, information for lightning strike survivors will be provided. On Saturday, lightning and wildfire information will be available.

When planning outdoor activities, check out the hazardous weather outlook and the latest forecast, which include thunderstorm and lightning potential. Make sure you get the specific forecast information of the location you will be visiting. The web sites for National Weather Service offices which cover Colorado and issue these products are…

Denver/Boulder…www.weather.gov/den Grand Junction….www.weather.gov/gjt Pueblo……………www.weather.gov/pub Goodland…………www.weather.gov/gld

NOAA’s lightning website which contains abundant information on lightning safety can be found at:

www.lightningsafety.noaa.gov

Lightning information specific for the State of Colorado can be found at: www.weather.gov/pub/lightning

The lightning topic for tomorrow will be the science of lightning.

Lightning Safety and Wildfire Awareness Series:

• Lightning Safety and Wildfire Awareness Week Introduction
• Lightning and wildfire safety overview
• The science of thunderstorms and lightning
• Outdoor lightning safety – When thunder roars, go indoors
• Indoor lightning safety – Staying safe in your home or office
• When lightning strikes – Rendering aid and the lasting effects of a strike
• Lightning and wildfires – Hand in hand hazards

Today we will see plenty of sun and the mercury is going to climb over the highs of the past couple of days. More notable however is the heat that arrives tomorrow and will hang around for a few days.

For today look for sunny skies to start the day and other than a few clouds this afternoon, there will be little interruption to the sunshine. Winds will be light and out of the east. The mercury will begin a steady climb this morning toward an afternoon high in the mid-80s. Overnight tonight skies stay clear and lows dip to around 60 degrees.

After today, high pressure will continue to build and the temperatures climb. Highs Tuesday, Wednesday and Thursday will be well into the 90s before we cool back down for Friday and the weekend.

Protecting yourself and your family from the dangers of lightning can be summed up in one phrase: When Thunder Roars, Go Indoors

Colorado is starting its annual Lightning Safety and Wildfire Awareness Week, an important opportunity to educate residents of the dangers lightning presents.  One statistic serves to highlight the very real hazard of lightning in Colorado – the Centennial State ranks as the second deadliest state for lightning fatalities in the nation.

We oftentimes read about the results of lightning strikes in our weekly look at Denver weather history.  They spark wildfires, cause property damage and injuries and in some cases result in death.  From 2001 to 2010 26 people were killed by lightning in Colorado – second only to Florida.

Each day during the National Weather Service’s Lightning Safety and Wildfire Awareness Week a new message is publicized covering a range of topics.  From lightning safety to the science of lightning, residents can learn more about this very real danger.

The following is the introductory message from the National Weather Service for this year with links to more information.  Education is key to protecting you and your family and we encourage you to study these pages and remember – When Thunder Roars, Go Indoors!

From the National Weather Service:

PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE BOULDER CO
600 AM MDT Sun Jun 18 2017

Governor John Hickenlooper has declared the week of June 18 through June 24 as Colorado Lightning Safety Awareness Week. Lightning strikes the ground in our state over a half million times each year and with many of us participating in outdoor activities, we need to learn how to protect ourselves from lightning hazards.

Lightning is also responsible for about half of the wildfires in Colorado each year. When lightning or other conditions are conducive to a high wildfire threat, the National Weather Service will issue Fire Weather Watches or Red Flag Warnings.

During this week a series of statements will cover a variety of topics related to lightning and wildfires.

Monday…Lightning Overview for Colorado
Tuesday…The Science of Lightning
Wednesday…Outdoor lightning safety
Thursday…Indoor lightning safety
Friday…Lightning medical issues for survivors
Saturday…Lightning and wildfires

Here are a couple web sites that contain additional lightning information.

NOAA`s lightning website which contains abundant information on lightning safety can be found at:  www.lightningsafety.noaa.gov

Lightning information specific for the State of Colorado can be found at: www.weather.gov/pub/lightning

Steve Hodanish
Senior Forecaster
NWS Pueblo, CO

June 18 to June 24: This week in Denver weather history

Heavy rain, flooding, lightning, tornadoes and hail are not at all uncommon this time of year and we see plenty of those types of events in our look back at this week in Denver weather history. Probably one of the most notable events occurred 10 years ago when a thunderstorms with large hail ripped through Denver International Airport causing $10 million in property damage and damaged dozens of airplanes.

From the National Weather Service:

1-30

In 2012…it was the hottest June in Denver since weather records began back in 1872. The average temperature for the month was 75.0 degrees which was 7.6 degrees above normal. There were a total of seventeen 90 degree days in the month of June. The highlight of record setting month was a stretch of five consecutive 100 degree days from the 22nd to the 26th. This was only the third time in Denver weather history in which this happened. Two of the high temperatures during the stretch peaked at 105 degrees…which set the all time record for the month of June and tied the all time maximum temperature for Denver.

17-18

In 1964…high winds at speeds of 50 to 60 mph with gusts as high as 75 mph caused damage to homes…power lines…and trees in Boulder. Non-convective west winds gusting to 46 mph caused some blowing dust at Stapleton International Airport on the 17th.

18

In 1875…a windstorm produced sustained winds to 45 mph during the morning hours. Numerous forest fires along the base of the mountains were visible from the city.

In 1886…northwest winds sustained to 40 mph were the strongest of the month that year.

In 1987…severe thunderstorms produced lightning…large hail… A tornado…heavy rain…and strong winds across metro Denver. Rainfall totaled 2.50 inches in an hour in Wheat Ridge… Causing minor flooding. I-25 was flooded in north-central Denver…snarling traffic. Hail 7/8 inch in diameter fell in Louisville with 1 1/2 inch hail near Golden and 1 to 1 3/4 inch hail in and near Castle Rock. A tornado touched down briefly in Castle Rock. No damage was reported. Lightning started a small fire that burned half a cabin near Evergreen.

In 1994…a funnel cloud was sighted over Aurora; hail to 1 3/4 inch diameter fell near Brighton; and hail over an inch in diameter fell over Aurora…southeast Denver… Louisville…and Boulder. Lightning struck a home in Henderson 9 miles north of Denver and knocked a hole in the roof…which caused the ceiling to collapse. Hail to 1 1/4 inch diameter was measured at Stapleton International Airport.

In 2002…the Hayman wildfire in the foothills to the southwest of Denver intensified…and the winds aloft carried the smoke plume directly over metro Denver…again creating a dense haze of smoke which blocked the sun. Surface visibilities were again reduced to as low as 1 1/4 miles at Denver International Airport.

In 2004…severe thunderstorms produced hail to 3/4 inch in diameter near Morrison…in Littleton…near Conifer…near Castle Rock…and in Aurora near Cherry Creek.

In 2013…a landspout tornado touched down at DIA. The tornado sent 10 thousand travelers on the concourse…on planes and in the terminal scrambling to get into tornado shelters. The tornado formed just to the south of Runway 35R and then moved slowly northwest between Runway 35R and 35L…and moved to within one third of a mile of Concourses A and B before dissipating. The tornado moved extremely close if not over the ASOS (Automated Surface Observation System) and another low level wind shear sensor at DIA. The ASOS weather observing system reported a 97 mph wind gust…while the wind shear sensor reported a wind gust to 109 mph at the same time indicative of an EF1 tornado. There was only minor damage noted to the equipment. Nine flights were diverted elsewhere during a tornado warning. Severe thunderstorms also produced large hail up to quarter size in Adams and Weld Counties.

In 2014…a severe thunderstorm produced large hail up to quarter size near Buckley Air Force Base.  At Denver International Airport…a peak wind gust to 55 mph was observed from the southwest…along with 0.37 inches of water.

19

In 1874…during the afternoon… Large columns of smoke from extensive fires in the mountain forests moved over the city from the west and southwest.

In 1875…while no precipitation was measured in the city… Rainfall over the Palmer Divide caused Cherry Creek to rise to the highest level in 10 years.

In 1977…hail up to 2 inch diameter damaged two patrol cars in Castle Rock.

In 1983 golf ball size hail fell just north of Bennett.

In 1990…lightning from a thunderstorm struck the roof of a house in south Boulder. Residents of the house were able to extinguish the ensuing fire with a garden hose…but not before several shingles had burned.

In 1992…thunderstorms produced hail up to 2 inches in diameter in central Douglas County near Castle Rock. Hail was 3 inches deep on I-25 south of Castle Rock. A funnel cloud was sighted near Parker.

In 1997…a 66-year-old man was knocked unconscious by a bolt of lightning while he was golfing at the eagle country club in Broomfield.

In 2000…dry microburst winds gusting to near 70 mph were reported across southeast Boulder and northern Jefferson counties. Peak wind gusts included: 68 mph at the national wind technology center…67 mph at Jefferson County airport… And 65 mph in Broomfield.

In 2001…severe thunderstorms produced large hail in the foothills southwest of Denver. Hail as large as 1 3/4 inch in diameter fell near conifer and Bailey.

In 2002…lightning damaged the Evergreen fire protection district radio repeater. One microwave transmitter…the main fire channel transmitter…and two solar panel controllers were destroyed. Lightning struck a garage and caused a small fire. Two vehicles parked in the garage were damaged. Hail to 3/4 inch in diameter fell near Castle Rock.

In 2004…severe thunderstorms produced hail to 3/4 inch in diameter near Castle Rock…Larkspur… And Golden.

19-21

In 1875…smoke from several large forest fires in the mountains was visible from the city on each of these days.

20

In 1888…northwest winds were sustained to 44 mph.

In 1956…a microburst caused a brief wind gust to 58 mph at Stapleton Airport.

In 1964…hail up to 1 inch in diameter was reported 1 mile north of Stapleton International Airport. A 3 minute hail storm at both Stapleton International Airport and lowry field piled small hail to one half inch deep.

In 1967…a strong thunderstorm dumped 1.95 inches of rain in less than an hour at Stapleton International Airport and produced a wind gust to 54 mph. The storm caused some flooding in east Denver and Aurora. There was widespread flooding to streets…basements… And store buildings and automobiles. Hail stones to 3/4 inch in diameter were measured at Buckley Field in Aurora. A tornado touched down just south of Littleton…damaging a barn and killing several head of cattle.

In 1985…a wind gust to 61 mph was reported at Golden Gate Canyon in the foothills west of Denver.

In 1986…a man was killed by lightning at Highlands Ranch south of Denver.

In 1987…several tornadoes were sighted across metro Denver. A tornado touched down briefly 5 miles west of Parker. A tornado was sighted just north of Chatfield Reservoir. A tornado just northwest of Watkins was on the ground for 15 minutes. A tornado near Barr Lake was taped by a television news crew. It had a double vortex and was on the ground for about 10 minutes. In addition to the 4 tornadoes…severe thunderstorms dumped large hail across metro Denver. One inch hail was reported in southeast Aurora; 3/4 inch hail fell at the Denver Technology Center…Buckley Field… And Franktown.

In 1992…several short-lived tornadoes occurred in the vicinity of Barr Lake. No injuries or damages were reported. A water spout was sighted over the southern end of Barr Lake. Funnel clouds were also sighted on the grounds of the rocky mountain arsenal by national weather service observers at Stapleton International Airport.

In 1994…hail up to dime size covered I-25 south of Denver and near Sedalia. Heavy rain caused local flooding on the interstate Highway.

In 1996…strong thunderstorm winds downed several large tree limbs in Boulder on the University of Colorado campus. A stop light in the city was also blown down.

In 1999…lightning sparked an oil tank fire near Brighton.

In 2001…large hail driven by strong thunderstorm winds raked Denver International and Front Range airports. Wind gusting to 54 mph along with hail as large 2 inches in diameter punched at least 14 thousand holes and cracks in the flat roofs of several buildings at Denver International Airport. In addition…93 planes and hundreds of cars were damaged. About 100 flights had to be cancelled…stranding 1500 travelers. The airport was completely shut down for about 20 minutes. The storm also damaged a ground avoidance radar used to track planes on the ground to prevent collisions. Damage was estimated at 10 million dollars…not counting the damage to the 93 airliners. The storm moved south and struck Watkins with hail as large as 2 1/2 inches in diameter and winds gusting to 60 mph. A least 30 private planes at Front Range airport were destroyed. The radome protecting the National Weather Service Doppler radar…which was tracking the storm…also sustained damage. The large hail…damaging winds… And heavy rain pummeled a mobile home park near Watkins. In the park…52 mobile homes… 14 recreational vehicles…3 homes… And a commercial building were damaged. Siding was riddled with holes and windows were broken. Vehicles sustained extensive damage and car windows were shattered. A handful of people were treated for minor cuts and bruises. The strong winds also flipped a tractor trailer along I-70 near Watkins. The storm caused power outages…which affected about 1200 residents. Excluding the damage at Denver International Airport…damage estimates totaled 49 million dollars…making the storm the costliest in the last 3 years and the 10th costliest since 1984. A small tornado touched down just east of Brighton… But did no damage. Hail as large as 2 inches in diameter fell near Fort Lupton with 3/4 inch hail measured in Bennett. Precipitation from the storm totaled only 0.23 inch at Denver International Airport.

In 2002…heavy rain fell near the Hayman wildfire burn area. Flash flooding washed out a 40-foot section of the access road to Cheeseman Reservoir. Some debris was washed against a gate…blocking the road. Hail to 1 1/2 inches in diameter fell near central city with 3/4 inch hail near Blackhawk.

In 2003…hail as large as 1 inch in diameter fell near Bennett and Strasburg with 3/4 inch hail measured in Denver…Golden… At Centennial Airport…and near Parker. Hail as large as 7/8 inch was reported in Arvada.

In 2004…a severe thunderstorm produced hail to 3/4 inch in diameter in and near Brighton.

In 2005…severe thunderstorms produced large hail near the palmer divide. Hail to 1 inch in diameter was measured near larkspur with 7/8 inch hail near Sedalia and 3/4 inch hail in Greenland. An apparent thunderstorm outflow produced a wind gust to 59 mph at Denver International Airport during the evening hours.

20-21

In 1897…high winds raked the city overnight. Southeast winds were sustained to 60 mph with gusts as high as 72 mph on the 20th. Southeast winds were sustained to 57 mph with gusts to 60 mph on the 21st.

In 2007…a brief hot spell produced two temperature records. The high temperature of 97 degrees was tied on the 20th. A new record high temperature of 99 degrees was established on the 21st.

21

In 1927…north winds were sustained to 40 mph with gusts to 44 mph.

In 1984…lightning struck and killed two children standing near a tree in a backyard in Lakewood. Strong thunderstorm downbursts caused a wind gust to 58 mph in Northglenn and knocked down two power poles near Brighton.

In 1988…lightning struck a home in Denver… Causing about ten thousand dollars damage. Lightning damaged 3 homes in Littleton…and also hit a house in greenwood village that had been struck by lightning 7 years previously.

In 1991…thunderstorms produced widespread hail across metro Denver. Hail as large as 2 1/2 inches fell at several locations across southwest metro Denver. One storm spotter reported hail 8 inches deep near the intersection of I-25 and c-470. Heavy rain with the storms caused some street flooding. In Commerce City…several cars were under water… And in Westminster a police officer reported water up to the doors of his car. Damage to homes and automobiles totaled 55 million dollars.

In 1992…a tornado touched down briefly near Bennett. Another tornado was briefly on the ground near Strasburg.

In 1994…heavy thunderstorm rains caused flooding in metro Denver. Several vehicles were stalled in the high water on I-25. Lightning struck an underground natural gas line in Aurora…causing a fire. Widespread power outages were also observed.

In 1996…three homes were struck by lightning in Parker. The lightning struck the garage of the first home…which started a small fire that burned some siding and spread into the attic. A second home sustained damage to the attic when a small fire was started. The third home received only minor damage. Lightning also sparked two small grass fires in the area. A man in Lakewood received minor injuries when he was struck by lightning while working on a ladder. A funnel cloud was sighted in Castle Rock. Strong thunderstorm winds downed a large tree near crossroads mall in Boulder. A small tornado (F0) briefly touched down near Lafayette. No damage was reported.

In 1997…one inch diameter hail was measured in Boulder.

In 2002…a thunderstorm wind gust to 62 mph was recorded at Denver International Airport.

In 2005…severe thunderstorms produced hail to 1 inch in diameter in Broomfield along with 3/4 inch hail near Arvada.

In 2006…a man riding a motorcycle was struck and killed by lightning on U.S. Highway 36 between church ranch blvd. And Sheridan Blvd in Westminster. After the biker was struck…he and his motorcycle crashed into the center concrete median of the highway. The lightning bolt left a crater in the highway asphalt that measured 18 inches long…8 inches wide and 4 inches deep.

In 2010…s severe thunderstorm produced hail up to 1 1/2 inches in diameter near Morrison. In Lafayette and Louisville…hail up to one inch in diameter was observed.

» Click here to read the rest of June 18 to June 24: This week in Denver weather history

June 12 to June 18: This week in Denver weather history

The first half of June is when Colorado’s severe weather season really kicks into high gear and our look back at this week in Denver weather history reflects that. Numerous flooding, hail, and tornadic events punctuate just how dangerous and damaging our weather can be this time of year.

From the National Weather Service:

1-30

In 2012…it was the hottest June in Denver since weather records began back in 1872. The average temperature for the month was 75.0 degrees which was 7.6 degrees above normal. There were a total of seventeen 90 degree days in the month of June. The highlight of record setting month was a stretch of five consecutive 100 degree days from the 22nd to the 26th. This was only the third time in Denver weather history in which this happened. Two of the high temperatures during the stretch peaked at 105 degrees…which set the all time record for the month of June and tied the all time maximum temperature for Denver.

10-11

In 1882…heavy thunderstorm rains on the morning of the 10th caused a rapid rise in dry creek…which enters the South Platte River at fairview in present day south Denver. This…combined with additional heavy rainfall on the 11th caused the South Platte River to overflow. Five people drowned and several houses were destroyed. Total losses in the city and suburbs was estimated at 75 thousand dollars. Total rainfall in central Denver was 2.21 inches over the 2 days.

In 2013…the high temperature of 99 degrees on the 10^th broke the previous record maximum temperature of 97 for the date.  Also…the minimum temperature of 68 and high temperature of 100 degrees on the 11th established a new record for highest minimum and maximum temperature for the date.

11

In 1947…a trace of snow fell over downtown Denver. Low temperature of 34 degrees was a record minimum for the date.

In 1962…hail caused extensive crop damage near Hudson northeast of Denver.

In 1970…stratiform rainfall totaled 3.16 inches at Stapleton International Airport. This was the greatest amount of precipitation ever recorded on a calendar day in June. In addition…it was the greatest amount of precipitation ever measured during any 24-hour period in June. The high temperature climbed to only 51 degrees…which was a record low maximum for the date.

In 1973…large hail from 3/4 to 1 1/2 inches in diameter fell west of Boulder.

In 1977…golf ball size hail was reported just south of Arapahoe County airport…now centennial airport. Lightning struck a home in Lakewood.

In 1988…a 30-year-old man was seriously injured by lightning while mowing his lawn in Denver.

In 1992…lightning started two house fires in the southern Denver suburbs where 3/4 inch hail fell and a funnel cloud was sighted.

In 1999…severe thunderstorms formed over the palmer divide and moved across Douglas…Elbert…and Adams counties. Hail as large as 1 inch in diameter was reported in and near Castle Rock…Sedalia…Franktown…and Aurora. Hail as large as golf balls accumulated several inches deep and caused a large section of a corrugated metal roof of a greenhouse complex to collapse near Franktown. About a third of the roof covering the 30 thousand square foot building collapsed. Thirty-five workers were trapped in the debris…but only 3 were treated for minor injuries. Hail 1 to 2 feet deep blocked the roadways and slowed the arrival of emergency vehicles. Damage to the building was estimated to be around 3 million dollars.

In 2006…a man was struck and killed by lightning as he was returning to his car after leaving the Mile High Flea Market near Henderson. Two others were knocked down…but not injured by the lightning strike. Severe thunderstorms produced large hail across the northern portion of metro Denver. Hail to 1 1/4 inches in diameter was measured in Arvada…with 1 inch diameter hail reported near Fort Lupton. Hail to 7/8 inch in diameter was recorded near Brighton…and hail…3/4 inch in diameter…fell near Keenesburg.

In 2009…large hail pummeled portions of Adams…Arapahoe… Elbert and Douglas counties. Hail up to 1 1/2 inches in diameter was measured near Parker.

In 2010…severe thunderstorms producing very large hail pummeled portions of Front Range foothills and urban corridor. The large hail ranged in size from 1 to 2 1/2 inches…caused extensive damage to home and vehicles. The hardest hit areas included: Brighton… Castle Rock…Greenland…Idledale…mountain view and Thornton. The combination of heavy rain and hail destroyed 50 thousand acres of cropland in southeast Weld County. Flash flooding forced the closure of State Highway 52…east of prospect valley. Several County roads were either flooded or completely washed out. At Denver International Airport…0.69 inches of rainfall was observed.

11-14

In 1999…damage from several hailstorms in and near metro Denver totaled 35 million dollars. About 17.5 million dollars was from automobile claims with another 17.5 million in homeowner claims. The areas hardest hit by the storms included Castle Rock…Commerce City…Evergreen… And Golden.

12

In 1901…south winds were sustained to 45 mph with an extreme velocity to 47 mph.

In 1917…northwest winds were sustained to 40 mph with gusts to 45 mph.

In 1927…flooding on Little Dry Creek in Englewood resulted in two deaths.

In 1947…a trace of snow fell over downtown Denver during the early morning. This was the latest last snow of the season (trace or more). This also marked the end of the longest snow season…264 days…from the first snow…a trace…on September 22…1946. High temperature of 43 degrees was a record low maximum for the date. Minimum temperature of 33 degrees was a record low for the date.

In 1971…a funnel cloud sighted over Arvada possibly touched down at the base of the foothills. The public reported 3/4 inch to 1 inch diameter hail over the city of Denver.

In 1974…strong thunderstorm winds caused damage to power lines in metro Denver. Northwest winds gusted to 45 mph at Stapleton International Airport.

In 1975…a thunderstorm wind gust to 56 mph was recorded at Stapleton International Airport.

In 1982…three small tornadoes were sighted near Bennett. One of the twisters caused minor crop and road damage along its path. A brief tornado was sighted by national weather service observers at Stapleton International Airport.

In 1983…3/4 inch hail fell in Boulder. Golf ball to 3/4 inch size hail fell in Arvada…denting cars and house roofs. Over a thousand hail damage insurance claims were filed from the area. Golf ball size hail also fell in Northglenn and Bennett…1 to 2 inch hail in Thornton…2 1/2 inch hail in northeast of Denver. A tornado was sighted 10 miles northeast of Stapleton International Airport; it was only on the ground for 1 to 2 minutes.

In 1984…large hail pelted many parts of southern metro Denver. Fifteen aircraft were damaged by golf ball size hail at Centennial airport. Golf ball size hail was reported in south Denver…and 3/4 inch hail was measured in southeast Aurora.

In 1987…a small weak tornado touched down for about 3 minutes near the intersection of I-70 and Colorado Blvd in northeast Denver. No damage was recorded. A microburst wind gust to 53 mph was recorded at Stapleton International Airport.

In 1991…in the city of Denver…lightning struck a tree under which seven people were picnicking. One person was critically injured. The others received only minor injuries.

In 1992…golf ball size hail fell in Evergreen.

In 1994…microburst winds gusting to 53 mph kicked up some blowing dust at Stapleton International Airport.

In 1996…lightning struck a house in Parker…which sparked a fire. The bolt was strong enough to blow nails out of the drywall in one room. About 85 percent of the house was damaged. No dollar estimate of the damage was available. Lightning also struck a power line in Boulder…which left 250 customers without electricity for a short time.

In 1997…a tornado touched down near Parker…damaging some construction equipment. Hail to 2 inches in diameter was measured in Henderson. One inch diameter hail fell in the city of Denver with 3/4 inch hail measured in Lakewood.

In 1999…hail as large as 1 1/2 inches in diameter struck Hudson. A funnel cloud was sighted by ramp personnel to the east of Denver International Airport.

In 2003…lightning blew a hole in the roof of a house in Highlands Ranch. The bolt knocked several holes in the bedroom ceiling and damaged the home’s electrical system.

In 2004…lightning struck a home in Louisville…but caused only minor damage.

In 2006…a strong microburst wind gust…estimated at 69 mph… Ripped the roof off a horse barn near the intersection of Havana Street and Smith Road in Denver. A 13 year old girl was injured…when she was thrown from a horse inside the barn at the time the roof was being torn off. A thunderstorm produced a microburst wind gust to 54 mph and a trace of rainfall at Denver International Airport. A severe thunderstorm produced hail to 0.75 inch near Watkins.

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In 2000…two large wildfires developed in the Front Range foothills as careless campers and very dry conditions proved to be a dangerous combination. Strong winds gusting in excess of 60 mph on the 13th fanned the flames… Spreading both wildfires out of control. Winds gusted to 78 mph atop Niwot Ridge near the Continental Divide west of Boulder. The Hi Meadows wildfire…about 35 miles southwest of Denver…consumed nearly 11 thousand acres and 80 structures…mostly high priced homes. The Bobcat wildfire…located about 12 miles southwest of Fort Collins… Consumed nearly 11 thousand acres and 22 structures. Late on the 16th…a strong cold front moved south over the great plains into northeastern Colorado. Low level upslope conditions developed in the wake of the front…producing 2 to 4 inches of snowfall overnight at elevations above 8 thousand feet. Firefighters were able to contain both fires shortly thereafter.

» Click here to read the rest of June 11 to June 17: This week in Denver weather history

Well, we hope you are ready for this. Our forecast for the three day period is very simply consistently hot and dry. For today look for sunny skies to start us off and continue throughout the day.

Temperatures will be climbing steadily and heading toward a high very close to the record for the date of 95 degrees. Skies will remain mostly clear tonight and we may see some slightly breezy winds after midnight. Overnight lows will be around 60 degrees.

Saturday looks to be a virtual repeat of today. Once again it will be sunny and dry and temperatures will climb to the low to mid-90s. Overnight Saturday it will be mostly clear with temps dipping to around 60 degrees.

Sunday brings some relief from the heat but not much. Temperatures will still be well above normal and close to the 90 degree mark.

Have a great weekend and keep an eye on the thermometer here.

Today we begin to settle into a bit more stable of a weather pattern. That stability will also come along with warmer temperatures, our warmest of the year thus far.

We start out today with clear skies then by mid to late morning will start to see a few clouds. By late afternoon expect some intrusion by them but then gradual clearing overnight. Right now we aren’t expecting any thunderstorms in our area today as they should be confined to the high country.

The main story for today is going to be the temperatures with highs pushing into the upper 80s. There is a chance we could record our first 90 degree temperature of the year. If we don’t today, we almost certainly will tomorrow. Look for lows tonight into the mid-50s.

Following our late thunderstorm last night, we see another chance for storms today. Temperatures will also begin a rising trend that will see us recording our first 90s before the end of the week.

We start out with mostly sunny skies then will see a gradual increase in cloud cover as moisture aloft increases. Temperatures will be mild today with a high in the low 80s.

There will be a good bit of instability which will help give rise to PM thunderstorms, particularly after about 3:00pm. The standard threats of wind, heavy rain and perhaps hail may be on the agenda. Much will depend on the cloud cover and whether it holds temperatures down thus limiting the convection needed to get things going.

Storms will subside this evening and be done by about midnight. Then we will see gradually clearing skies and lows overnight in the mid-50s.

Looking ahead, the trend is going to be toward warmer mercury readings for the balance of the week. We’ll be close to 90 degrees tomorrow then well into the 90s Thursday and Friday before cooling a few degrees Saturday. Get more details in our extended forecast here.

May 29 to June 4: This week in Denver weather history

The first part of June typically brings some of Denver’s most eventful weather of the year and we clearly see that in our look back at this week in Denver weather history. From many damaging hail and wind events to heavy rains that resulted in flooding and even the Southlands Mall tornado of 2009 it has been an eventful week in history.

From the National Weather Service:

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In 1977…unusually warm weather for this early in June resulted in 3 maximum temperature records being equaled at the time: 88 degrees on the 1st…90 degrees on the 2nd… And 93 degrees on the 4th. Maximum of 91 degrees on the 3rd was not a record.

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In 2012…it was the hottest June in Denver since weather records began back in 1872. The average temperature for the month was 75.0 degrees which was 7.6 degrees above normal. There were a total of seventeen 90 degree days in the month of June. The highlight of record setting month was a stretch of five consecutive 100 degree days from the 22nd to the 26th. This was only the third time in Denver weather history in which this happened. Two of the high temperatures during the stretch peaked at 105 degrees…which set the all time record for the month of June and tied the all time maximum temperature for Denver.

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In 1989…heavy rain drenched metro Denver with the greatest amounts recorded on the 3rd. Total rainfall ranged from 1 1/2 to 3 inches. Roads were washed out in Boulder County… And flooded basements caused water damage to houses in the Gunbarrel section of Boulder. In suburban Denver…heavy rain caused minor flooding along Lena Gulch in Jefferson County where two mobile home parks were evacuated. Rainfall totaled 1.66 inches at Stapleton International Airport.

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In 1921…heavy rainfall for nearly a week…on top of streams already swollen by mountain snowmelt…produced widespread flooding over the South Platte River basin…including the tributaries through the canyons to the west and southwest of Denver. Heavy rainfall over the 6-day period totaled 3.36 inches in Boulder…4.98 inches in Morrison…4.27 inches in Castle Rock…and 2.94 inches in the city of Denver. Rainfall amounts in the foothills were estimated between 3 and 6 inches. The narrow-gage tracks of the Colorado and southern railroad were destroyed in the Platte Canyon. From the mouth of the canyon through the city to near Brighton… The river spread from 1/2 to nearly 1 1/2 miles wide… Flooding farm and pasture land and destroying or damaging many bridges. In the city…many businesses along with as many as 500 homes were inundated…forcing their evacuation. Bridges were swept away. The high waters flooded the rail yards and stock yards in lower downtown…closing three adjacent packing houses. The heavy rains also caused flooding on Boulder creek in Boulder on the 6th.

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In 1904…a thunderstorm during the early morning of the 3rd turned into widespread general rain…which continued into the early afternoon of the 4th. Rainfall totaled 2.04 inches.

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In 1878…a “waterspout” or cloudburst of rain was sighted up the South Platte canyon at around noon. The resulting high waters on the South Platte River slightly damaged a railroad bridge in the city.

In 1937…a trace of snow fell in downtown Denver where rainfall totaled 0.25 inch. Minimum temperature of 34 degrees was a record low for the date. Northeast winds were sustained to 22 mph.

In 1951…the start of the second shortest snow-free period on record…109 days…occurred with the last snow of the season…a trace…on the 3rd. The first snow of the next season occurred on September 21st when 4.2 inches of snow fell at Stapleton Airport.

In 1954…a microburst produced brief sustained winds of 40 mph with gusts as high as 64 mph at Stapleton Airport.

In 1956…the failure of the Georgetown dam caused downstream flooding on clear creek at Idaho Springs and Golden.

In 1976…funnel clouds were sighted near Brighton…Erie…and Dacono…all north of Denver. A tornado touched down briefly 1 1/2 miles east of Lafayette. Another tornado touched down briefly at Hyland Hills Golf Course in Westminster. No damage was reported.

In 1983…severe thunderstorms during the afternoon produced 3/4 inch hail in south Denver…golf ball size hail 5 miles west of Parker…1 1/4 inch hail in Littleton…1 1/2 inch hail in south Aurora.

In 2001…hail as large as 1 inch in diameter fell 17 miles north of Bennett in Adams County.

In 2005…snow was mixed with rain for nearly an hour at Denver International Airport during mid to late morning. The temperature at the time was 45 degrees. Precipitation totaled 0.36 inch for the day. Northwest winds gusted to 37 mph.

In 2008…a severe thunderstorm produced large hail…up to 1 3/4 inches in diameter in Arvada…a northwest suburb of Denver. Several vehicles were damaged. In addition…a severe thunderstorms produced hail to 1 inch in diameter… 10 miles northeast of manila…east of Denver International Airport.

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In 1965…lightning and an 18-hour rain storm damaged streets and roads and telephone and power lines across metro Denver. Precipitation totaled 2.77 inches at Stapleton International Airport where the visibility was reduced to 3 miles at times from pre-frontal thunderstorms and heavy upslope rains.

In 1998…a late season snow storm struck the Front Range foothills. Up to 5 inches of snow fell in Coal Creek Canyon. Light snow also fell over western sections of metro Denver and briefly at Denver International Airport. Snow covered the grass at the Denver federal center in Lakewood before melting around mid-morning on the 5th. No snow fell at the site of the former Stapleton International Airport. Several temperature records were set. High temperatures of 47 degrees on the 4th and 49 degrees on the 5th were record low maximums for their respective dates. Minimum temperature of 34 degrees on both the 5th and 6th were record lows for those dates.

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In 1864…high water on the west fork of clear creek caused a small dam near empire to fail…which destroyed several downstream bridges.

In 1885…a windstorm during the afternoon and early evening produced south to southwest winds at sustained speeds up to 42 mph.

In 1937…a trace of snow fell in downtown Denver. This was the latest snowfall of record at the time. Light rain and snow were mixed around mid-day. Precipitation totaled only 0.01 inch. North winds were sustained to 20 mph.

In 1941…hail of unknown size fell on the city.

In 1961…lightning struck and injured an airman outside a base classroom at Lowry Air Force Base. Funnel clouds were sighted near Frederick and firestone north of Denver. The one near Frederick briefly touched down in an open field but caused no damage. Heavy rain and hail hit the Fort Lupton area causing damage to crops. Heavy rain in Frederick added to the flood damage of the 3rd. A pilot reported a funnel cloud that touched down briefly and then dissipated south of Castle Rock.

In 1965…a lightning-caused fire destroyed a mountain home near Rollinsville.

In 1988…a tornado touched down 5 miles east of Lafayette near I-25 and stayed on the ground for 15 minutes. The twister hit a campground…demolishing one trailer and damaging six others…along with 4 cars. The rope-like funnel also blew down fences…signs…and electrical boxes. The twister moved a 1500-pound hay wagon 150 feet. Total damage to the campground was estimated at 50 thousand dollars. Another tornado touched down between Broomfield and Lafayette…staying on the ground for about 20 minutes. The twister hit a subdivision…unroofing one abandoned house and causing minor damage to a dozen others. A four- car garage and three barns were destroyed. At one location a chain link fence…a satellite dish…and a shed were destroyed…while the deck and garage of the house were damaged. A grain storage tank was moved 200 feet. There were reports of boards being blown through walls; one came through a kitchen.

In 1992…lightning struck a 15-year-old boy…causing minor injuries…in Adams County 6 miles north-northeast of Stapleton International Airport. Thunderstorm winds gusted to 63 mph at Jefferson County Airport near Broomfield…to 58 mph at the U.S. Atomic Energy Commission’s facility at Rocky Flats…to 58 mph in Thornton…and to 48 mph at Stapleton International Airport where 1/8 inch diameter hail fell.

In 1996…strong microburst winds up to 60 mph damaged several trees in Boulder…snapping large branches 1 to 2 inches in diameter.

In 1997…a woman was struck by lightning as she was walking to her car in Nederland. The lightning bolt apparently struck a nearby power line and arced into her left hand. She received minor injuries.

In 2014…severe thunderstorms broke out across parts of Arapahoe…Douglas…Elbert and Jefferson Counties… impacting areas generally southwest and south of Denver. The storms produced large hail…from quarter to golfball size.

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In 1977…lightning caused several power outages and moderate damage to a railroad building.

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In 1954…thunderstorm winds at speeds of 50 mph with gusts as high as 59 mph briefly reduced the visibility to 1 mile in blowing dust at Stapleton Airport.

In 1967…the public reported golf ball to 1 3/4 inch diameter hail in the city…3 miles west-southwest of Stapleton International Airport. The amount of damage was unknown. Thunderstorm winds gusted to 46 mph at Stapleton International Airport.

In 1981…hail to 3/4 inch in diameter was reported in east Denver.

In 1990…golf ball size hail was reported near Strasburg on I-70 east of Denver.

In 1991…a tornado was spotted by national weather service personnel and weather spotters…14 to 17 miles northeast of Stapleton International Airport. A funnel cloud was sighted over south Aurora just east of Buckley Field…and a tornado was spotted just east of Watkins. No damage was reported. Thunderstorms moved through Aurora and dropped hail up to 1 inch in diameter. The storms also produced heavy rain… Up to 1 inch in 30 minutes…causing flooding of streets. Water was reported hood deep…stranding motorists. Water covered fire hydrants at some intersections.

In 1995…a waterspout sighted over Standley Lake in northern Jefferson County…quickly dissipated once it reached shore. A brief tornado…which was momentarily visible by a dust debris cloud on the ground…damaged the roof of a house in Westminster. A funnel cloud was sighted just south of Lafayette. Hail from 3/4 to 1 1/4 inches in diameter fell over north Boulder. Thunderstorm outflow produced north wind gusts to 44 mph at Denver International Airport.

In 1997…a tornado touched down near baseline reservoir just east of Boulder. The tornado struck a home…tearing off part of the roof. A storage building nearby was nearly leveled and 5 trees were uprooted. The twister then moved onto baseline reservoir…forming a huge waterspout. Several recreational vehicles and a boat dock were also damaged. A nearly stationary line of thunderstorms dumped 4.60 inches of rain on portions of Thornton. Extensive flooding of streets and underpasses and other low lying areas was reported. Several businesses were flooded and basements in the area were damaged. Rainfall totaled 1.02 inches at Denver International Airport and 1.24 inches at the site of the former Stapleton International Airport. Large hail…up to 1 3/4 inches in diameter…fell over the city of Denver with 3/4 inch hail measured in Littleton and near Henderson.

In 1999…high winds developed for a brief time in and near the foothills of Boulder. The Gamow Tower on the University of Colorado campus recorded a wind gust to 87 mph. Winds peaked to 71 mph atop Niwot Ridge near the continental divide west of Boulder.

In 2003…a small tornado touched down near Strasburg…but did no damage.

In 2012…severe thunderstorms broke late in the evening…striking areas hardest from Denver southward. Locations impacted by the storms included but were not limited to: Aurora…Castle Rock…Centennial…Highlands Ranch…Lone Tree…Parker and Surrey Ridge. The storms produced a barrage of
large hail…damaging straight line winds…flash flooding and several short lived tornadoes. The hail ranged in size from 1 to 2 inches in diameter…and caused extensive damage to homes and automobiles. The hail inundated the roadways with several inches of hail in Douglas County. Consequently…snow plows had to be called out to clear the roadways. The combination of torrential hail and heavy rain produced flash flooding in parts of Elbert…Douglas and Arapahoe Counties…as thunderstorms brought up to 3.35 inches of rain to some areas within 90 minutes. In Aurora…Picadilly Road was closed from flooding north of 6th Avenue. A water rescue took place on South Gun Club Road in Arapahoe County…where floodwaters were rushing to depth of 3 feet. Flash flooding forced the closure of several streets and roads from Parker south to The Pinery…where the floodwaters inundated the roadway with up to 2 feet in several locations.  At Centennial Airport…a historic B-17 Flying Fortress suffered extensive damage as hailstones as large as ping pong balls struck the aircraft. Although the airframe itself did not require repair…the fabric-covered ailerons and elevators were extensively damaged. The hail came straight down and punched holes in the fabric-covered control surfaces. The aircraft landed just hours before the storm hit to participate in a weekend tour stop.  Lightning also struck two homes…one in Lakewood and the other in Parker. Straight line winds downed trees and power lines in Aurora. As a result…scattered electrical outages affected around five thousand residents.  At Denver International Airport…0.61 inches rainfall was recorded along with a peak wind gust of 41 mph.

6-7 » Click here to read the rest of June 4 to June 10: This week in Denver weather history