Weather History

August 18 to August 24: This Week in Denver Weather History

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This Week in Denver Weather History

Our look back at this week in Denver weather history highlights the extreme weather that can be visited upon us this time of year. Many of the events showcase severe weather more associated with spring than the latter half of summer.

From the National Weather Service:

16-19

In 1979…heavy thunderstorm rains on each of 4 consecutive days dumped a total of 2.62 inches of rain on Stapleton International Airport. The heaviest rain…1.05 inches… On the 19th was accompanied by 1/4 inch diameter hail.

18

In 1965…heavy rain in areas south and east of Denver caused some flooding in Littleton and Englewood. Clear creek was running near bankfull…and heavy rain in southwest Denver flooded intersections.

In 1966…a brief very heavy thunderstorm dumped 0.61 inch of rain in just 5 minutes at Stapleton International Airport. Total rainfall from the storm…0.64 inch…fell in just 10 minutes. Half inch diameter hail also fell at Stapleton International Airport. The public sighted funnel clouds 10 to 15 miles south of the airport.

In 1967…hail struck in a strip along the eastern foothills and caused minor damage in Boulder. Hail accumulated to a depth of 4 to 6 inches in Jefferson County just southwest of Denver.

In 1983…one inch to hen egg size hail was reported in Broomfield with golf ball size hail at Northglenn.

In 1990…dime size hail and thunderstorm wind gusts to 50 mph were reported by storm spotters just east of Aurora near the intersection of Mississippi Avenue and Gun Club Road. The hail and strong winds damaged a number of windows in the area.

In 1991…very heavy rain from slow moving thunderstorms dumped up to 3 inches of rain in 20 minutes in the vicinity of Idaho Springs and Central City. Flooding in Idaho Springs forced the closure of the Virginia Gulch Road…which runs from Idaho Springs to Central City. Dirt roads above Central City were damaged or destroyed with the mud being swept onto streets in town. High water in Clear Creek…up to 3 feet above flood stage…washed out a bridge in Idaho Springs. Rock and mud slides forced the closure of I-70 about 1 mile east of Idaho Springs.

In 1997…dry microbursts produced two peak wind gusts to an estimated 60 mph east of Buckley Field.

In 2000…hail as large as 3/4 inch in diameter was measured 5 miles west of Sedalia.

In 2003…a severe thunderstorm produced hail as large as 2.75 inches in diameter at Highlands Ranch. Hail to 3/4 inch was reported in Aurora near Cherry Creek and in Arapahoe County 9 miles southeast of Aurora.

In 2004…heavy thunderstorm rainfall caused flash flooding across central and southern metro Denver. A rain gage at City Park recorded 4.37 inches of rainfall from the deluge. Several roads in and around the city had to be closed due to floodwaters…stranding many vehicles. The Denver fire department conducted at least 15 water rescues. One driver nearly drowned when he made a wrong turn into a retaining pond. Four men who witnessed the accident were able to save the man before his car was completely submerged. Widespread street flooding was reported in the Denver Stapleton area where rainfall totaled 3.81 inches. Standing water over 6 inches deep was reported near I-70 and Quebec…I-225 south of I-70…and I-25 near 6th Avenue. Flood waters reached 8 feet deep in some low lying areas as sewers became clogged and the storm runoff pipes were unable to handle the heavy flow of water. Heavy rainfall caused additional flash flooding south of Denver. Several street intersections in Centennial and southern Aurora became impassable due to high water. Two feet of water covered portions of the roadway near Park Meadows Mall. One person had to be rescued near the intersection of Arapahoe Road and Liverpool. Floodwaters forced the closure of Stonegate Parkway near Jordan Road and Lincoln Avenue. Flooding was also reported on Meridian Blvd. near I-25. Rainfall was 1.62 inches at Denver International Airport.

18-19

In 1875…nearly 0.75 inch of rainfall in the city overnight… Possibly assisted by heavier rainfall upstream…produced a decided and rapid rise in Cherry Creek…which washed out some bridges. Other small creeks and streams were filled to overflowing.

19

In 1983…heavy rain fell across the northern metro Denver suburbs with 1.50 to 1.80 inches of rain in Broomfield… Arvada…and Thornton.

In 1989…lightning killed a 31-year-old man and injured his 10 year old nephew when it hit a tree they were walking under in the foothills about 5 miles west of Boulder. The boy received mouth to mouth resuscitation on the scene and recovered after being hospitalized overnight. Three other people were knocked to the ground by the bolt…but were uninjured.

In 1990…3/4 inch diameter hail was reported in Wheat Ridge. A thunderstorm over west Denver dumped an inch of rain in 20 minutes…causing minor street flooding. One inch diameter hail was reported over east Denver. Ping pong to golf ball size hail was reported 14 miles northeast of Denver at the intersection of 122nd Ave. and Brighton Blvd. The hail stones knocked out windows and did an unspecified amount of damage to the roof of a house. Close by…heavy thunderstorm rains caused gullies…irrigation ditches…and small streams to overflow their banks near the intersection of 120th Avenue and Riverdale Road. Flood waters 1 to 2 feet deep covered the river bottom land along the South Platte River. However…no structures were threatened by the flood waters.

In 1999…heavy rain…up to 5 inches in two hours…caused east tollgate creek to jump its banks. The bike path adjacent to the creek was underwater at several locations. Several underpasses were also flooded…halting traffic. In addition…an unfinished playground at a local elementary school was completely flooded. Lightning struck a vehicle at East Evans Avenue and Tower Road. The woman inside the vehicle was not injured.

In 2016…a severe thunderstorm produced a wind gust to 64 mph near Commerce City.

19-30

In 1875…grasshoppers appeared in great numbers at 10:00 am on the 19th. Thousands landed on the ground. The streets were literally covered with them. Swarms of grasshoppers were seen on each day. All gardens in the city were devastated…and in the countryside the grasshoppers were very destructive to ripened grain. On the 30th the grasshoppers were so numerous as to almost darken the sun.

20

In 1980…winds to 55 to 60 mph were recorded in south Boulder.

In 1982…strong thunderstorm winds blasted the Jefferson County Airport near Broomfield…causing an estimated 3 million dollars in damage. At least 5 hangars and 15 airplanes were damaged…many seriously; one hangar was completely destroyed. Torrential rains accompanied the winds. Heavy rains also dumped on Boulder where 1.65 inches fell in just 15 minutes…causing street flooding. Wind gusts to 72 mph were recorded in Boulder. Over half an inch of rain fell in just 5 minutes in Littleton where two homes were struck by lightning. Lightning also struck a house in Arvada where over an inch of rain sent Ralston Creek over its banks. Strong winds accompanied the storms.

In 1984…slow moving thunderstorms dumped 1.25 inches of rain in Evergreen…causing street flooding. A half inch of rain fell in just 18 minutes in southeast Denver. Littleton and Boulder were also drenched with about an inch of rain. Rainfall totaled 0.92 inch at Stapleton International Airport.

In 2001…severe thunderstorms produced damaging winds and large hail across metro Denver. Hail as large 1 inch in diameter fell in Aurora near Cherry Creek. Strong thunderstorm winds gusting as high as 58 mph blew the roof from a building between Thornton and Denver and toppled several trees in Denver. One tree landed on a mail truck. Other thunderstorm winds were clocked to 60 mph near Parker… 62 mph in Broomfield…and 61 mph at Denver International Airport.

In 2006…a tornado (f0) touched down near Bennett…but caused no reported damage.

In 2013…severe thunderstorms pounded the southern Denver suburbs and other parts of the Front Range. In Jefferson County…water rescues were reported for some people in stranded cars. In the Ken Caryl area…large hail from one inch to 1 3/4 inches in diameter was reported. On West Chatfield Avenue in Jefferson County…hail runoff gathered six inches deep in spots and “hail plows” were sent out to clear some streets. Hail up to one inch in diameter was also reported near Castle Rock.

Continue reading August 18 to August 24: This Week in Denver Weather History →

Climatology, Thornton Weather

Denver ties record high temperature for August 17

Record High Temperature

Another high temperature record is in the books for the Mile High City. As measured at Denver International Airport, Denver hit a high temperature of 98 degrees. This ties the record high for August 17 last set in 2020.

Here in Thornton, we were actually warmer with a high of 99 degrees. At Stapleton, where historical Denver weather records were taken from 1950 to 1995, the high was only 93 degrees.

Climatology, Colorado Weather, Thornton Weather

NOAA’s fall outlook predicts warmer and drier than normal conditions for Colorado

NOAA CPC Fall 2024 Temperature Outlook (NOAA)
NOAA CPC Fall 2024 Temperature Outlook (NOAA)

Tired of the heat of summer? Well, don’t power off that air conditioner just yet.

NOAA’s Climate Prediction Center’s autumn outlook for September, October and November, if accurate, would have us continue the above normal, drier than normal conditions of recent months.

The forecast gives above normal chances for most of the contiguous United States to see above average temperatures. For Colorado, the Four Corners region has the greatest chance at a likeliness of 60 to 70 percent. Most of the state, including the Front Range, is at a 50 to 60% chance.

In terms of precipitation, a good chunk of the nation has good chances to see below normal levels. The vast majority of Colorado is being given a 40 to 50% probability of below normal levels.

NOAA CPC Fall 2024 Precipitation Outlook (NOAA)
NOAA CPC Fall 2024 Precipitation Outlook (NOAA)Seasonal
Weather History

August 11 to August 17: This Week in Denver Weather History

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This Week in Denver Weather History

Colorado’s unofficial severe weather season may be over but August holds a wide variety of related weather hazards that can be damaging and deadly. Looking back at this week in Denver weather history, flooding, large hail and even tornadoes have made appearances in our past.

From the National Weather Service:

8-13

In 1875…clouds of grasshoppers were seen flying through the air on the prevailing winds during each day.

11

In 1872…fog was very dense until about 8:00 am. There was water dripping from the roofs of houses as if it had rained. The rain gage showed 0.01 inch of moisture…even though there had been no rainfall.

In 1927…an apparent dry microburst produced only a trace of rain and brief northwest winds sustained to 34 mph with gusts to 44 mph.

In 1980…hail up to golf ball size caused some roof and car damage in the southern part of Aurora.

In 1990…lightning ignited a storage tank filled with 10 thousand gallons of crude oil in a farmer’s field near Dacono…25 miles north of Denver. Flames shot to 40 feet high for nearly 2 hours before being extinguished. A lightning bolt also struck 21 miles north of Denver at an Erie fire station…causing extensive damage to the gas meter and electrical system. The sudden power surge blew out the station’s television set…a refrigerator…and a pop machine. Small fires spread throughout the structure… Totally destroying the building’s electrical wiring. The fires were quickly extinguished by the in-resident fire fighters. Golf ball size hail was reported in Denver near the intersection of Santa Fe Drive and I-25.

In 2012…a severe thunderstorm produced a wind gust to 60 mph at rocky mountain metropolitan airport.

In 1992…dime size hail fell in Westminster.

In 1994…strong thunderstorms produced large hail across northwest and north metro Denver. One inch diameter hail fell in Brighton with 3/4 inch hail reported in Westminster and at Indian Hills in the foothills west of Denver. Lightning struck a house in Arvada. The resulting fire destroyed one-third of the house. Funnel clouds were sighted over Westminster.

In 1997…large hail…strong winds…and torrential rains hammered portions of Lakewood and south Denver. Nearly 1 inch of rain fell in the span of 10 minutes in south Denver with a storm total of 1.81 inches. Street flooding was extensive as gutters and other drainage systems in the area were clogged by hail…piled several inches deep…and other debris. Strong thunderstorm winds to 50 mph and large hail accompanied by heavy rain caused extensive damage to cars…homes…and businesses. Several trees were downed by the strong winds…and trees were stripped of their leaves by hail. A water lily exhibition on display at the Denver botanic gardens was heavily damaged. Final estimates of the damage included 60 million dollars to automobiles and an additional 68 million dollars to homes and businesses. Hail to 1 1/2 inches in diameter fell in south Denver with 3/4 to 1 inch hail in Lakewood. A man received minor injuries in Aurora when he was struck by lightning while talking on the telephone.

In 2003…hail to 3/4 inch in diameter was measured in Aurora near Cherry Creek.

12

In 1876…the temperature climbed to a high of 100 degrees in downtown Denver.

In 1941…excessive thunderstorm rainfall flooded streets and delayed traffic for a few hours in some sections of the city. The basements of a considerable number of homes and commercial buildings were flooded. The total value of the damage was unknown. Only 0.94 inch of thunderstorm rainfall was recorded downtown.

In 1969…a man and a 9-year old boy were injured…when lightning struck a tree near where they were standing. Both were revived after treatment…but the boy later died of respiratory failure due to electrical shock.

In 1984…heavy thunderstorm rains drenched southern metro Denver. Rural roads in Douglas County received minor washouts. Hail…as large as 3/4 inch in diameter…was reported in southeast Aurora with one inch diameter hail reported near Parker. Rainfall totaled 1.00 inch at Stapleton International Airport.
12-13 in 1975…heavy rains caused flash flooding along the foothills from Denver north. Thunderstorm rainfall totaled 1.56 inches at Stapleton International Airport.

In 2004…a brief cool spell resulted in two daily temperature records. The low temperature of 49 degrees was a record minimum for the 12th…as was the low temperature of 48 degrees on the 13th.

13

In 1959…thunderstorm winds gusted to 53 mph at Stapleton Airport.

In 1983…thunderstorms dumped torrential rain in Northglenn… Thornton…and Broomfield. Northglenn was drenched with 1.72 inches in 30 minutes. Street flooding was widespread. Hail…as large as 3/4 inch in diameter…was reported 7 miles northeast of Boulder along with heavy rain which caused some street flooding.

In 2000…lightning sparked 3 small grass fires near Golden. The fires were quickly contained. Hail as large as 3/4 inch in diameter fell in Castle Rock.

In 2019…Hail up to 1 3/4 inches in diameter was observed 4 miles west of Frederick…with hail up to one inch in diameter near Dacono.

14

In 1960…a bolt of lightning struck a man in Henderson… Causing serious burns.

In 1962…the temperature climbed to a high of 100 degrees at Stapleton Airport.

In 1968…a young man on a golf course in Denver was injured when lightning struck a tree under which he was standing. Lightning caused minor damage to a house in Denver. Heavy thunderstorm rain caused local street flooding. One inch diameter hail fell at Jefferson County Airport near Broomfield.

In 1973…winds as high as 85 mph damaged 20 aircraft at the Arapahoe County airport…now Centennial Airport.

In 1977…three tornadoes were sighted in Bennett. A man suffered a broken leg when hit by a flying board. He was outside his camper home…which was destroyed. All windows were broken in a near-by farmhouse where some shingles were ripped off and a 2 car garage was knocked down. Several vehicles were damaged and a cat…some rabbits…and chickens were killed. A broken oar from a boat was driven into the side of a house. A mobile home was overturned. One old barn was destroyed. Half a dozen homes and several agricultural buildings were damaged just west of State Highway 79.

In 1978…high winds produced much blowing dust…causing many traffic accidents in the Denver-Boulder area. Winds gusts of 70 to 101 mph were recorded. Northwest winds gusted to 44 mph at Stapleton International Airport.

In 1980…lightning hit two power poles in Littleton…causing 400 dollars in damage. Rainfall of 1.23 inches in a short time caused minor flooding…which included damage to a ground floor apartment and partially submerging a few vehicles in water. Thunderstorm rainfall totaled 0.98 inch at Stapleton International Airport.

In 1983…2.10 inches of rain drenched Golden in an hour with similar amounts in Lakewood and Boulder. Over ten thousand dollars’ worth of plants were washed away at a nursery in Lakewood.

In 1997…twelve motorists were injured in a multi-car accident when strong microburst winds estimated to 50 mph blew blinding dust across I-70 near Bennett.

In 1998…lightning struck a hydro-electric plant in Nederland… Causing a power outage. Residents in the foothills west of Boulder…including Nederland…Ward…Eldora…Jamestown… and Gold Hill…were without power for about an hour.

In 2006…heavy thunderstorm rainfall near Deckers washed away some the banks along State Highway 67 between Deckers and Westcreek. Several driveways on both sides of the highway were also damaged.

Continue reading August 11 to August 17: This Week in Denver Weather History →

Thornton Weather

Part 3: Does it matter if Denver weather and climate records are skewed?

Two airports, two different climates. How Denver's weather and climate records are skewed by a 12 mile move. (ThorntonWeather.com)
Two airports, two different climates. How Denver’s weather and climate records are skewed by a 12 mile move. (ThorntonWeather.com)

ThorntonWeather.com’s owner and operator used to write for a now-defunct website called Examiner. This was a national site but with locally focused content. As the Denver Weather Examiner, Tony covered a number of topics related to Denver and Colorado weather.

Among them, he was always quick to point out how Denver’s weather records were being skewed by the move of Denver’s official weather station to Denver International Airport. In 2009, he wrote a three-part series explaining why this was an issue and why it mattered.

Fifteen years later, this continues to be a problem and thus we are re-publishing the series here. While the data is not current and some of the images were lost with time, readers can still understand and appreciate the problem.

Part 3: Does it matter if Denver weather and climate records are skewed?
Originally published March 5, 2009, Examiner.

Fourteen years ago Denver opened its new airport and the National Weather Service followed suit and moved Denver’s weather monitoring system 12 miles east further onto the plains.  Since then, weather enthusiasts and meteorologists have said Denver’s climate records were forever being altered inappropriately.

Monday we provided some background on the history of Denver’s weather monitoring and records.  Yesterday we took a look at empirical data that shows that the weather at DIA does not accurately reflect the weather in town where people actually live and showed why it isn’t fair to compare data from the last 14 years to measurements taken in the previous 124.  Today we explain why all this matters and talk to the National Weather Service to see what  they have to say about the problem.

Does it matter?

Public policy decisions are made based on accurate measurements of our environment and the weather.  Consider the debate over global warming or something on a smaller scale closer to home, water management decisions.  Living in a semi-arid environment like we do in Colorado, much depends on water- from Colorado’s largest industry of agriculture to how much water you have for your lawn in the summer.  If measurements taken at DIA claim an abnormally dry or wet year, governments and the public make decisions based on them.  But are those decisions accurate and are they based on valid data?

I spoke to Byron Lewis, Program Manager at the National Weather Service Office in Boulder, and he stated that he felt the comparison of historical records between those taken at DIA and Stapleton should not matter – he says it is no different than when Denver’s official station moved from downtown to Stapleton in 1950.  He also felt that the issue of accuracy between precipitation and snow measurements was not noteworthy.

Others see it differently.  They point to the fact that the move from downtown to Stapleton was 6 miles – half the distance of the move from Stapleton to DIA.  Further, they argue that the area where DIA resides in a much more ‘plains’ type climate and does not accurately reflect Denver weather.

One retired NWS meteorologist told me, “It is climatologically absurd for the NWS to mix the 1872-1994 Denver city records with DIA weather data for the purposes of normals, record extremes, and top ten lists.  Many in the public and science community can recognize this fallacy–and it’s making the Weather Service look foolish.”

The Solution

The National Weather Service does at least partially recognize the problem and seems to have acknowledged that the weather at DIA is not what most folks experience within Denver.  Mr. Lewis said that next month they hope to begin installing a new monitoring station in Denver City Park.  This new station will provide more accurate measurements closer to where people actually live.  However, there is a catch – official Denver records and measurements will continue to be taken at DIA.

There is nothing to prevent the National Weather Service from moving the official measuring site back to Stapleton or some other more central location.  One local news station has a statement on their website claiming that, “because commercial airports are the origin of regular weather observations in the United States. This is mandated by the National Weather Service and the Federal Aviation Administration.”  This is absolutely untrue.

While weather stations must be maintained at major airports for obvious reasons, cities do not need to use those specific stations for their official measurements.  In fact, the United States’ two largest cities – New York and Los Angeles – both take official weather measurements in different locations than their airport.  New York measures its weather in Central Park and Los Angeles takes its measurements downtown.

It is this weather enthusiast’s opinion that by throwing yet another location into the mix, the water simply gets muddled further.  As long as Denver’s “official” weather measurements are taken at DIA, any records should either come with an asterisk denoting that they aren’t comparable to historical records or they should only be based on data collected in the last 14 years.

Unless and until a move is made, we just have to remember to take any announcement of a weather record with a grain of salt.

Two airports, two different climates. Read the series:

Thornton Weather

Part 2: Data shows Denver weather records skewed by move to DIA

Two airports, two different climates. How Denver's weather and climate records are skewed by a 12 mile move. (ThorntonWeather.com)
Two airports, two different climates. How Denver’s weather and climate records are skewed by a 12 mile move. (ThorntonWeather.com)

ThorntonWeather.com’s owner and operator used to write for a now-defunct website called Examiner. This was a national site but with locally focused content. As the Denver Weather Examiner, Tony covered a number of topics related to Denver and Colorado weather.

Among them, he was always quick to point out how Denver’s weather records were being skewed by the move of Denver’s official weather station to Denver International Airport. In 2009, he wrote a three-part series explaining why this was an issue and why it mattered.

Fifteen years later, this continues to be a problem and thus we are re-publishing the series here. While the data is not current and some of the images were lost with time, readers can still understand and appreciate the problem.

Part 2: Data shows Denver weather records skewed by move to DIA
Originally published March 3, 2009, Examiner.

Did you hear February was Denver’s least snowiest month?  Or was it?  As we discussed yesterday, a growing chorus of voices are objecting to the National Weather Service’s use of measurements at Denver International Airport for official Denver weather record keeping.  They claim that comparing data from DIA to previous records compiled for more than 40 years at Stapleton and more than 75 years before that in downtown isn’t a fair analysis.

In this second of a three part series, we take a look at some of the data to see just how big of a difference the 12 mile move from Stapleton to DIA made.  We also investigate potential issues with accuracy at the automated monitoring station at DIA that could forever be altering our climate records.  Tomorrow we will take a look at why all of this matters and why you should care.

Temperatures

An analysis shows that in just the last eight years DIA registers warmer high temperatures and cooler low temperatures than stations closer to downtown and in areas where people actually live.  For our comparison, we compared the last eight years of data for Denver International Airport versus the measurements taken at Buckley Air Force Base.  We chose Buckley because that is the closest official measuring station to the location of the old Stapleton International Airport.

<insert table>

As you can see, the differences between where measurements have been taken for the last 14 years at DIA and where they were taken previously is significant.  DIA’s highest recorded temperatures each year averages nearly 2 degrees more than those closer to Denver.  Similarly, the station’s low temperatures are more than 2 degrees cooler.  This essentially throws any record high or record low temperatures that were recorded in the last 14 years out the window.  Any comparison of today’s data with historical records taken at Stapleton are invalid because the location move to DIA has clearly impacted the measurements.

Precipitation

This is probably the single most astonishing statistic and helps to show just how much of a difference 12 miles can make.  The National Weather Service has been taking precipitation measurements at both DIA and at the former Stapleton site so we can do a direct comparison between the two sites.  The results are astonishing.

<insert table>

The chart clearly shows that precipitation measurements at DIA consistently underperform as compared to those at Stapleton.  Over the 8 year period, DIA on average measures 13% less precipitation than Stapleton.

One year in particular stands out.  In 2002 Colorado was in a drought by any measurement.  At the end of the year the National Weather Service proclaimed it as Denver’s driest on record.  However, that claim was based on measurements at DIA.  If you use the measurements at Stapleton – where weather records were kept for more than 40 years – the claim doesn’t stand up to scrutiny.  Stapleton’s 8.49 inches of precipitation in 2002, while certainly a dry, below normal year, would actually make it only the 6th driest year.  It can easily be argued that the claim that 2002 was Denver’s driest year should be discarded.

As a more recent example, March 2008 was proclaimed the “third driest March on record” when a mere 0.17 inch of precipitation was recorded at DIA.  However, 0.55 inch was recorded at Stapleton, an amount which would not put the month anywhere near the top 10 driest.

Snowfall

Historical snowfall measurement comparisons between the two locations unfortunately cannot be directly performed as it was only this year that the National Weather Service began measuring snow at DIA.  However, we can infer from the precipitation measurements noted above that there will be a comparable discrepancy in snowfall measurements as well.  This stands to reason as the plains receive less snow than areas closer to the mountains and going 12 miles east can make a big difference.

Issues of accuracy?

The precipitation and snowfall issue gets even further convoluted this year with the move to measuring snowfall at DIA.  While this would seem to solve the problem of inconsistency between taking precipitation measurements at DIA but snowfall at Stapleton, it turns out things aren’t quite that easy.

Weather enthusiasts have noticed problems with recent snowfall and precipitation measurements.  Just recently on Monday, January 12th, when a small snow storm moved through the Front Range the National Weather Service recorded 3 inches of snowfall but only 0.03 inch precipitation.

On average snow has a 10:1 moisture content which means that 1 inch of snow equals 0.1 inch of moisture.  Using the standard, approximately 0.3 inch precipitation should have been recorded – 10 times what was actually reported.

Extending the observation period out to include the two month period from December 1, 2008 to January 31, 2009, similar problems have occurred.  At Stapleton, where measurements are taken manually, 12 inches of snowfall was recorded with a moisture content of 1.08 inches – approximately an 11:1 ratio and one that could be expected.  By contrast, DIA – using automated precipitation measurements – recorded 15 inches of snow but a meager 0.37 inch of precipitation.  That is an unfeasibly dry 40:1 snow to precipitation ratio.

Detractors abhor the use of automated stations for such important climate records and are quick to point out that this is but one of many examples of inconsistent measurements.  One former NWS employee said, “the NWS sold their soul to automation years ago” and as a result we are stuck with inaccurate records.

Two airports, two different climates. Read the series:

Climatology, Thornton Weather

Part 1: Do Denver weather and climate records have an asterisk attached?

Two airports, two different climates. How Denver's weather and climate records are skewed by a 12 mile move. (ThorntonWeather.com)
Two airports, two different climates. How Denver’s weather and climate records are skewed by a 12 mile move. (ThorntonWeather.com)

ThorntonWeather.com’s owner and operator used to write for a now-defunct website called Examiner. This was a national site but with locally focused content. As the Denver Weather Examiner, Tony covered a number of topics related to Denver and Colorado weather.

Among them, he was always quick to point out how Denver’s weather records were being skewed by the move of Denver’s official weather station to Denver International Airport. In 2009, he wrote a three-part series explaining why this was an issue and why it mattered.

Fifteen years later, this continues to be a problem and thus we are re-publishing the series here. While the data is not current and some of the images were lost with time, readers can still understand and appreciate the problem.

Part 1: Do Denver weather and climate records have an asterisk attached?
Originally published March 2, 2009, Examiner.

February 2009 is Denver’s least snowiest February on record.  A new record high temperature is recorded on January 21, 2009.  Record low temperatures are recorded on December 14th and 15th of last year.

These announcements are common and we all take notice when we hear them and they make for great water cooler chat topics but are these claims accurate?

In 1995 Denver finally opened its new airport out on the plains east of the city.  This new facility, 12 miles as the crow flies northeast of the old Stapleton International Airport, moved the airport from an urban environment to a rural one and more than 19 miles from the center of Denver.  Following that move, the National Weather Service (NWS) began taking some of its official measurements at the glistening new airport.  In doing so, some say Denver’s climate records have forever been altered and as such any weather record should have an asterisk attached to it.

Official Denver weather statistics were collected from the NWS’ downtown Denver office from November, 1871 to December 1949.  In January 1950 observations were moved to Stapleton International Airport where they remained until February 1995.  From March 1995 forward, Denver’s official weather has been measured at DIA.  With the move, precipitation switched to Automated Surface Observing Systems (ASOS), an automated means of making the measurement.  In a somewhat confusing twist, the measuring of snowfall remained at Stapleton until just this snow season.

Map:

http://maps.google.com/maps/ms?ie=UTF8&hl=en&msa=0&ll=39.819612,-104.886475&spn=0.337528,0.594635&z=11&msid=118280686911175493835.0004640da10c79cdcdba0

The question many are asking – Does a move of 12 miles make that much of a difference when measuring the weather?  Twelve miles is the same distance as between downtown and Golden, or downtown and Centennial or downtown and the northern edge of Thornton.  How often do we hear about heavy snow falling at I-25 and C-470 and yet downtown remains dry?  If you live in any of the outer metro area suburbs you know that what the news stations report as the weather downtown rarely is what you experience.

Twelve miles, particularly in a topographically and geographically diverse area as the Front Range would appear to make a world of difference.  That is why when you watch the evening news local meteorologists include the conditions at their local station downtown in addition to the official data at DIA.  Most local meteorologists have railed against the move and are quick to point out that the weather as measured at DIA does not reflect what Denver weather truly is.

When new records are announced, detractors point out that it isn’t fair to compare the data compiled at DIA with that which was recorded previously at Stapleton or downtown.  Just yesterday the National Weather Service announced that February 2009 was the least snowiest on record.  But was it really?  The NWS says Denver received only a trace of snow (less than 0.1 inch) but this was at DIA.  The vast majority of the metro area had at least some measurable snow during the month and Stapleton, where official records were kept for more than 40 years, had 0.8 inch of snow – a number that would push it well out of ‘least snowiest’ contention.  Many say we are comparing apples and oranges.

Empirical data shows that every meaningful statistic has been skewed by the move to DIA.  In this three part series we will take a look at how moving Denver’s official weather measurements to DIA have skewed Denver’s climate records and why it matters to you.  Tomorrow we take a look at the empirical data showing just how big of a difference 12 miles makes.  Wednesday we’ll tell you why it matters and learn about some possible solutions to the problem.

Stay tuned!

Two airports, two different climates. Read the series:

Colorado Weather, Natural Disasters, Weather History

100 years ago – Colorado’s deadliest tornado on record

Images from the Rocky Mountain News showing the devastation after a tornado struck near Thurman, Colorado on August 10, 1924.
Images from the Rocky Mountain News showing the devastation after a tornado struck near Thurman, Colorado on August 10, 1924.

The National Weather Service did a fantastic writeup about this devastating event on August 10, 1924 that claimed the lives of 11 people, 9 of which were children. It is a fascinating read. Check it out here.

From Microsoft Copilot:

The 1924 Thurman Tornado is the deadliest tornado in Colorado’s history. Here are some key details:

The tornado remains a significant event in Colorado’s weather history due to its devastating impact on the small community.

Climatology, Thornton Weather

July 2024 weather recap: Another warm one, precip comes in close to average

Thornton, Colorado's July 2024 temperature summary. (ThorntonWeather.com)
Thornton, Colorado’s July 2024 temperature summary. (ThorntonWeather.com)

Certainly, in our minds, July 2024 was a very warm one as it seemed like the 90+ degree days just kept on coming. Average temperatures did come in a good bit above normal. Precipitation wasn’t anything extraordinary and while it ended up close to average, the last half of the month was quite dry.

High pressure was the dominating force for the majority of the month with only intermittent breakdowns of the ridge. As a result, overall hot and dry conditions were the general rule. There were, however, just enough effects from some cold fronts to keep average temperatures relatively in check.

The last 10 days saw only one day with precipitation leading to dry conditions across the Colorado Front Range. This resulted in numerous wildfires in the foothills and smoke blanketing the area for several days.

Thornton’s average temperature for the month was 74.9 degrees. This was a good bit warmer than our running 18-year average for the month of 73.8 degrees. This made July 2024 the sixth warmest July over that period. Temperatures ranged from a maximum of 102 degrees on July 12th down to a low of 50.7 the morning of the 4th.

The Mile High City, as measured at Denver International Airport, came in a good bit warmer with an average mercury reading of 75.7 degrees. This was just a bit above Denver’s long term July average of 75.1 degrees. Denver set record highs on the 12th and 14th (102 and 101 degrees respectively) and tied the record high of 99 degrees on the 29th.

In terms of precipitation, Thornton received 1.74 inches during the month. Nearly half of that coming over two days on the 20th and 21st (0.80”). The total fell short of our running average for the month of 1.95 inches.

Denver’s official rainfall total for the month came in at 1.10 inches. This was well below the city’s July average of 2.14 inches.

Click here to view Thornton’s complete July 2024 climate summary report.

Thornton, Colorado's July 2024 precipitation summary. (ThorntonWeather.com)
Thornton, Colorado’s July 2024 precipitation summary. (ThorntonWeather.com)
Weather History

August 4 to August 10: This Week in Denver Weather History

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This Week in Denver Weather History

The beginning of August typically continues our monsoon season. This leads to increased chances for thunderstorms with heavy rain and the associated hazards that come with it. Our look back at this week in Denver weather history highlights the dangers of flooding, hail and lightning and even includes reference to grasshopper swarms being blown into the city.

From the National Weather Service:

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In 1988…two inches of rain fell in 3 hours at both Morrison and Wheat Ridge. Thunderstorm rainfall totaled 0.80 inch overnight at Stapleton International Airport.

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In 1889…southwest winds were sustained to 42 mph with an extreme velocity to 52 mph.

In 1924…0.01 inch of rain fell over downtown Denver. This along with the 0.01 inch of rainfall on the 10th was the only rainfall of the month…the driest August on record.

In 1963…heavy rains in the foothills above Idaho Springs caused mud and rock slides which closed U.S. Highways 6 and 40 for a time.

In 1976…hail to 1 inch diameter was reported 12 miles southwest of Denver. Hail to 3/4 inch in diameter was reported in Lakewood. Small hail…1/4 to 1/2 inch in diameter…fell at Stapleton International Airport.

In 1982…heavy rain poured through the roof of a clothing store in Aurora…causing widespread water damage. The roof was being repaired when the storm hit.

In 1983…hail up to one inch in diameter fell in Aurora where heavy rain produced street flooding.

In 1984…a Colorado state trooper was struck and injured by lightning in Northglenn.

In 1989…a microburst wind gust to 52 mph was recorded at Stapleton International Airport.

In 1997…lightning sparked a small fire in a home in Arvada… Causing minor damage. Several intersections in both Arvada and Westminster were flooded by thunderstorms producing heavy rain. Several cars were damaged by the high waters… And a number of businesses were flooded.

In 1999…flooding and flash flooding problems developed over metro Denver as slow moving thunderstorms dumped from 2 to 3.5 inches of rainfall in about 3 hours. Near the junction of I-25 and U.S. Highway 36…up to 4 feet of water flooded an auto dealership. About 45 cars were ruined. Damage estimates to the dealership alone totaled nearly a half million dollars. Sections of I-25 and U.S. 36 near the interchange were closed due to floodwaters. Floodwaters… Up to 5 feet deep…forced the evacuation of two mobile home parks in federal heights. Railroad tracks were washed out near Federal Blvd. and 64th avenue. Numerous power outages caused widespread blackouts in Thornton and Littleton. Along Massey Draw near Carr St. and Chatfield Reservoir…4 homes were flood damaged and portions of their backyards washed out. Widespread street flooding was also reported in Boulder where several buildings were flood damaged…including the University of Colorado Memorial Center.

In 2004…two golfers were shocked when lightning struck the eighth green of the golf course at Castle Pines north of Castle Rock. The two men suffered only minor injuries. Heavy thunderstorm rain from the same storm caused flash flooding. Floodwaters rushed across parts of U.S. Highway 85 near the entrance to the Castle Pines Golf Club. The traffic lanes were covered with up to 6 inches of running water.

In 2008…lightning sparked a grassfire that consumed 300 acres on the northern edge of Green Mountain…in Jefferson County. Gusty winds and very dry conditions allowed the wildfire to quickly spread and threaten several houses. Fortunately…only minor damage was reported to homes due to smoke and melted siding.

In 2018 a severe thunderstorm produced strong winds in and around Denver. A peak wind gust to 60 mph was observed near Firestone with a gust to 59 mph near Buckley Air Force Base. A peak wind gust to 40 mph from the southwest was observed at Denver International Airport.

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In 1881…the low temperature cooled to only 76 degrees…the record high minimum temperature for the month.

In 1889…southwest winds were sustained to 42 mph.

In 1918…hail pelted the city…but was light and caused no damage. Precipitation totaled 0.25 inch. Northwest winds were sustained to 31 mph.

In 1964…lightning struck two boys in Denver while playing ball. One was treated and released from the hospital…but the other boy suffered second degree electrical shock and cardiac arrest and was hospitalized in critical condition for several days.

In 1969…two tornadoes touched down briefly in an open field southeast of Buckley Field in Aurora. No damage was reported.

In 1970…heavy rain in the Indian Hills area in the foothills west of Denver caused flash flooding…which washed out roads and damaged other property. Hail accumulated to a 3 inch depth with stones up to golf ball size; however…most of the damage was from flooding.

In 1982…2.38 inches of rain fell in an hour in Arvada… Causing minor flooding on Ralston Creek. In Westminster… 1 1/2 inches of rain fell…causing damage to streets and culverts. In addition…lightning caused some minor power outages across metro Denver.

In 1983…very heavy thunderstorms hit the southern portion of metro Denver. Heavy rainfall…as much as 2.89 inches in 38 minutes…caused widespread street flooding in southeast Denver. Two feet of water covered a section of I-25. Hail up to golf ball size accompanied the storm in Littleton and Englewood…along with 60 mph winds.

In 1984…a heavy thunderstorm drenched Littleton with up to 2.35 inches of rain in an hour…along with small hail that piled up to 2 inches deep. Flood waters were up to 4 feet deep in parts of town with many basements flooded. There were some power outages caused by lightning.

In 1990…a thunderstorm dumped 1.25 inches of rain in 12 minutes near tower and smoky hill roads in southeast Aurora. Minor street flooding was reported in the area.

In 1992…a pilot reported two funnel clouds near Cheery Creek Reservoir. Both dissipated quickly. Dime size hail fell near Franktown.

In 1994…one inch diameter hail fell near Strasburg. No damage was reported.

In 1999…a dog kennel east of Denver International Airport… Was flooded when a small dam…upstream in Elbert County… Was breached. The floodwaters…up to 4 feet deep…washed away some 6-foot fences and other small buildings. Ten of the 70 dogs boarded at the kennel drowned.

In 2002…a mail carrier was struck by lightning as he inserted a key into a multi-unit mailbox in Bailey. The shock knocked the man back against the mail truck. He suffered minor injuries. Lightning struck a residence in Commerce City. The resulting fire destroyed the roof of a detached garage and damaged much of its contents. Hail as large as 1 3/4 inches in diameter pelted Pine. One inch diameter hail fell in Arvada and southwest Denver. Heavy rain triggered a mudslide along U.S. Highway 285 near Bailey. Both lanes of traffic had to be closed until debris could be removed from the highway. Several residences in the Bailey and Glenisle areas were also flooded.

In 2004…heavy thunderstorm rainfall caused localized flash flooding in Virginia Canyon near Idaho Springs. Sections of the Virginia Canyon Road had to be closed due to the floodwaters.

In 2008…a severe thunderstorm produced large hail…up to 1 1/4 inches in diameter…northeast of Parker. Several automobiles were damaged.

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