Thornton, Colorado, USA
UpdatedSun, 18-Nov-2018 5:25am MST 


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Thornton’s weekend starts with seasonal conditions, will end cooler and possibly wetter

Friday, June 22nd, 2018 5:03am MST

A pretty good three day period ahead for us. Friday and Saturday will offer temps near normal and some chances for storms while a cold front arrives cooling things down Sunday.

For today, look for some cloud cover throughout the day but overall mostly sunny skies. Temperatures will top out in the mid-80s. The afternoon brings a slight chance for thunderstorms. Further east, the plains will have a much greater chance for storms, some of which will turn severe. Tonight, skies will clear with low temperatures dipping to the mid-50s.

Saturday will offer up sunny skies for most of the day then a few clouds in the afternoon and evening. High temperatures again will be in the mid-80s. The evening again brings slight chances for a thunderstorm. Saturday night, lows again drop to the mid-50s.

A cold front moves in Saturday night and that will offer a chance in the pattern Sunday. We’ll see increased cloud cover with highs in the mid to upper 70s. Some sprinkles of rain may be seen in the morning then an increase in coverage, perhaps with some thunder, in the afternoon into Sunday evening.

Have a great weekend!

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Astronomical summer begins, starts with the longest day of the year

Thursday, June 21st, 2018 5:04am MST
On the June solstice, the Earth’s northern hemisphere is tilted at its maximum toward the sun. The result is the longest day of the year for the northern part of the planet. (NASA)

On the June solstice, the Earth’s northern hemisphere is tilted at its maximum toward the sun. The result is the longest day of the year for the northern part of the planet. (NASA)

Astronomical summer arrived in Thornton this morning and with the solstice we will enjoy our longest day of the year.

Summer officially began at 4:07am MDT this morning.  The Summer Solstice occurs when the North Pole is tilted at it closest to the sun – 23.4 degrees.  This results in the longest day of the year in the Northern Hemisphere.

Here in Denver the sun rises at 5:32am today and sets at 8:31pm.  This will give us 14 hours, 59 minutes and 14 seconds of daytime.

Tomorrow it will be a bit less than one second shorter than today and each day from now through the Winter Solstice in December will get gradually shorter as well.

At the poles of the globe, the seasonal extremes will be quite notable.  Areas north of the Arctic Circle to the North Pole will see 24 hours of daylight and have a midnight sun.  On the opposite end of the globe, the South Pole will have no direct sunlight at all as they are in the depths of their winter.

Did you know that there is a difference between the astronomical seasons that we are discussing here and meteorological seasons?

Meteorological seasons differ slightly and are geared toward matching the calendar with the annual temperature cycle. This is done primarily for meteorological observing and forecasting and in many ways it is more logical than the astronomical seasons.

For the Northern Hemisphere, the meteorological spring covers the months of March, April and May. Summer brings the hottest months of the year and so meteorological summer is June, July and August. Meteorological fall then is September, October and November followed by the coldest months of December, January and February as meteorological winter.

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First day of summer to bring seasonal temperatures, calm conditions

Thursday, June 21st, 2018 4:56am MST

Summer arrived this morning at 4:07am and Mother Nature is welcoming it in fine fashion. Thornton will enjoy a quiet day with temps right near average for the date.

We start out with clear skies above and those will be with us through the morning. Some clouds will arrive this afternoon and evening. Temperatures will be topping out right near the average high for the date of 84 degrees.

Tonight, skies will be partly clear with lows in the mid-50s.

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Comfortable temperatures, only a slight chance for storms for Thornton’s Wednesday

Wednesday, June 20th, 2018 4:59am MST

We have a very nice looking day ahead for us, one that skips the drama of the past couple of days.

Mostly sunny skies start things off and will be with us into the early afternoon. After that, there will be a bit of an increase in cloud coverage.

Winds will be light most of the day then a bit breezy in the mid to late afternoon as thunderstorms start to pop up around us. High temperatures today will be in the mid-70s, a range that will be just about perfect.

Thunderstorm activity today will be primarily confined to the high country and foothills but there is just a slight chance something could sneak out onto lower elevations.

Today, skies will be partly clear with lows around 53 degrees.

Have a great day!

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June 17 to June 23: This week in Denver weather history

Tuesday, June 19th, 2018 2:11pm MST
This week in Denver weather history

June 17 to June 23: 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:


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.


In 1965…on the afternoon and evening of the 16th…violent thunderstorms produced extremely heavy cloudbursts of rain over the palmer divide and sent a wall of water as high as 20 feet down both branches of plum creek into the South Platte River and through metro Denver. The heavy rainfall produced the most devastating flood in the history of Denver. Rainfall totaled 14.0 inches in 3 hours at both Larkspur and Palmer Lake with 12.0 inches recorded in Castle Rock. The flood waters caused extensive damage to roads and bridges in Larkspur…Castle Rock…and Sedalia…including washing out the I-25 bridge over east Plum Creek in Castle Rock. The citizens of metro Denver received reports of the flooding to the south and had a few hours to initiate evacuation procedures along the South Platte River…greatly limiting the loss of life. By evening…the flood reached Littleton where an heroic effort was made to save nearly 150 horses at the Centennial racetrack…which was completely inundated by the flood waters. As the flood proceeded through the city of Denver…the river became more than 1/2 mile wide and destroyed all homes…trailer courts… And businesses in its path. The waters contained debris ranging from refrigerators to old cars. As many as 26 bridges were damaged or destroyed…including the 6th avenue freeway bridge across the South Platte. Both Public Service Company power plants were shut down by the flood. The King Soopers grocery chain bakery was inundated. About midnight… The torrent crested at 25 feet above normal with flow exceeding 40 times normal and is the record flood on the South Platte and many of its tributaries. The flood caused 230 million dollars in damage and 8 deaths along the entire South Platte River basin. The intense rain also caused flooding along Cherry Creek in Denver…on Toll Gate and Sand creeks in east metro Denver…and on Kiowa and Bijou creeks to the east of Denver. The South Platte River flood closed nearly every major east-west highway into Denver…nearly isolating the city. The flood caused heavy damage to state and County roads in the area. Railroads were also hard hit with the main yards in lower downtown inundated. Sewerage… Water supply facilities…and irrigation works also received heavy flood damage. The flood crest did not reach Nebraska until the 20th.


In 1915…northwest winds were sustained to 41 mph with an extreme velocity to 42 mph.

In 1967…this was the 24th consecutive day with a trace or more of precipitation from May 25th. Precipitation totaled 5.87 inches during the period…more than a third of the average yearly total.

In 1975…hail more than 2 inches in diameter fell in eastern Aurora.

In 1977…golf ball size hail was reported 3 miles east of Arapahoe County Airport…now Centennial Airport. Heavy hail to 3/4 inch in diameter was reported in Littleton… Castle Rock…and Sedalia.

In 1979…a man and a girl were struck and killed by lightning while walking in a park in northwest Denver.

In 1987…3/4 inch hail fell near Boulder.

In 1991…a microburst wind gust to 59 mph kicked up some blowing dust at Stapleton International Airport.

In 1998…hail as large as 3/4 inch in diameter fell in Boulder.

In 2003…lightning struck a feeder line…knocking out the electricity to about 3000 residents in Littleton. A lightning strike caused minor damage to the roof and attic of a home in Lafayette. Another lightning strike caused minor roof damage to a residence in Louisville. Yet another lightning strike hit a home in Denver and caused a small attic fire. Hail as large as 1 inch in diameter was measured near Centennial airport and near Greenland.

In 2009…hail up to 1 inch in diameter was measured near Longmont.


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.


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.

» Click here to read the rest of June 17 to June 23: This week in Denver weather history

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Tuesday brings cooler temperatures, another chance for storms

Tuesday, June 19th, 2018 5:07am MST

Following on yesterday’s hailstorm, cooler temperatures will arrive today. The afternoon brings a chance for another rain of storms, some possibly severe if conditions set up right.

We start out under cloudy skies and some light drizzle. By mid-morning some clearing will begin to be seen but still with a good bit of cloud coverage.

This afternoon thunderstorms may again roll, particularly after 2:00pm. If we get enough daytime heating to kick convection off, these once again could turn severe with strong winds and damaging hail.

Highs today will top out in the low to mid-70s.

Tonight, thunderstorm activity should be tapering off by 9:00pm, ending by midnight. Skies will be mostly cloudy with lows in the low to mid-50s.

If you have any pics of hail damage, please share them and we will get them added to our slideshow. Be sure to keep an eye on our Severe Weather Briefing Page for all the latest.

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Thornton’s workweek starts out with seasonal temps, good chance for storms

Monday, June 18th, 2018 5:10am MST

Finally! Thornton was slow to see the rain yesterday but some did finally arrive overnight. Today, begins damp, will then see some clearing, then see a decent chance for storms.

Mostly cloudy skies will be above initially but soon after the clouds will begin to clear off. Mostly sunny skies can be expected for the mid-day period then an increase in coverage again in the afternoon as storms build. Temperatures will be topping out today right around the 80 degree mark.

As for those thunderstorms, after about 1:00pm scattered activity is expected to develop and last through the evening. Some of these storms will have the potential to turn severe with large hail, strong winds, and heavy rain so please do keep an eye out and be aware.

Tonight, some rain will be possible after midnight. Overnight lows will dip to the mid-50s.

We’re going to continue to enjoy temperatures close to or a bit below normal for the first half of the week. Then we expect to see some drying and warming for the latter part. Get more details in the extended weather forecast here.

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Thornton’s weekend weather starts hot, ends cooler and with a good chance for rain

Friday, June 15th, 2018 5:11am MST

The three day period starts off with a continuation of the unseasonably warm weather of recent days. However, by the end of the weekend, we see much-needed relief in the form of cooler temps and rain.

For Friday, mostly sunny skies will be above with the afternoon bring an increase in cloud cover. Temperatures once again will climb, leading to a high in the low to mid-90s. A slight increase in moisture brings a bit better chance of thunderstorms in the mid to late afternoon. Tonight, skies will be mostly cloudy with lows dipping to the low 60s.

Saturday starts to bring about change as moisture from the remnants of Tropical Storm Bud arrive in Colorado late in the day. The day starts with some sun then will see an increase in cloud cover leading to mostly cloudy skies for the latter part of the day. Temperatures will top out in the mid-80s by noon then start to cool. We’ll see an increased chance for storms, particularly in the evening hours. Some rain and storms may continue overnight Saturday night. Look for lows Saturday night into Sunday morning around the 60 degree mark.

Sunday bring significant changes. Cloud cover will be pretty solid for the day and temperatures cool with highs in the mid to upper 70s expected. Some light showers may be seen earlier in the day but in the afternoon, chances increase significantly. We could see some good, soaking rain at that time, lasting into the evening.

Have a great weekend!

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Thornton’s Thursday to offer hottest temps of the year, some breezy winds

Thursday, June 14th, 2018 4:57am MST

The heat kicks into high gear today with an increase of a few degrees over the already hot temps we saw yesterday. We also will see some breezy PM winds and just a slight chance for an evening storm.

We start out under mostly sunny skies with cloud cover increasing as we head toward noon. Partly sunny skies will be the rule for much of the day. Winds will be light this morning then pick up a bit and by mid-afternoon become breezy and out of the northeast.

As for temperatures, they won’t be inhibited much by the cloud cover. Look for highs to top out around 98 degrees.

This evening we stand just a slight chance for a thunderstorm but with little moisture to work with, we aren’t giving much of a chance.

Tonight, partly cloudy skies will be above, lows will drop to the lower 60s.

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June 10 to June 16: This week in Denver weather history

Wednesday, June 13th, 2018 1:57pm MST
This week in Denver weather history

June 10 to June 16: This week in Denver weather history

We are entering the primetime of Colorado’s severe weather season. Our look back at Denver weather history for this week shows numerous damaging, dangerous and deadly weather events.

From the National Weather Service:


In 1864…high water from melting snow combined with heavy rains over the upper reaches of the South Platte River forced the river over its banks and caused flooding of low lying areas along the river in the city. The amount of rainfall in the mountains and in the city is unknown.


In 1943…a man was killed by lightning while using a surveying instrument at Buckley Field.

In 1969…hail stones 2 to 3 inches in diameter caused extensive damage to buildings and automobiles in an area from northeast of Boulder to Longmont. Two funnel clouds were reported near Castle Rock. A funnel cloud and 1 inch hail stones were reported 10 to 20 miles southeast of Stapleton International Airport. Hail stones to 1 3/4 inches fell 3 miles west of Littleton. Hail to 3/4 inch diameter fell over southeast Denver.

In 1988…thunderstorm winds clocked to 60 mph unroofed a porch and downed a fence at a home near Stapleton International Airport. A small tornado touched down briefly in northeast Aurora. Another small tornado touched down for 3 minutes in southeast Aurora. No damage was reported from either twister.

In 1989…a national weather service observer saw lightning strike 2 storage tanks at 40th and Havana…3/8 mile northeast of Stapleton International Airport. The strike temporarily knocked out some weather observing equipment at the national weather service.

In 1991…a tornado was sighted 2 miles south of Castle Rock. No damage was reported. The funnel cloud associated with the tornado was sighted for 5 minutes by National Weather Service observers at Stapleton International Airport.

In 1994…lightning struck a home in Denver…which started a fire in the attic and caused minor damage.

In 1997…lightning struck a security guard at the castle pines golf course near Castle Rock. He received only minor injuries.

In 1999…severe thunderstorms rolled off the foothills over metro Denver…producing large hail and damaging winds. Hail to 1 inch diameter fell near Evergreen with 1 3/4 inch hail measured west of Golden. Hail to 1 1/2 inches fell in Commerce City with one inch hail in Lakewood…wheat ridge… The city of Denver and at Denver International Airport where thunderstorm winds gusted to 58 mph. As the storms moved east…3/4 inch hail was reported in Aurora…and damaging thunderstorm winds developed between Bennett and Strasburg. Winds gusting as high as 69 mph blew half a metal roof from a shed in a Bennett lumberyard. A small barn was also leveled between Bennett and Strasburg. Winds also gusted to 58 mph near Manilla.

In 2000…a dry microburst produced a wind gust to 58 mph at Jefferson County Airport. Thunderstorm winds gusted to 55 mph at Denver International Airport.

In 2003…hail as large as 1 3/4 inches was measured at centennial airport and near Parker.

In 2005…hail to 7/8 inch in diameter was reported near Parker with 3/4 inch hail measured near Castle Rock.

In 2009…lightning struck an apartment complex…a veterinary hospital in Boulder and caused minor damage. Lightning also struck two oil tanks…one in Boulder and the other at Front Range airport north of Watkins. The oil tanks in both instances were set on fire and suffered extensive damage.

In 2010…a complex of severe thunderstorms hammered portions of eastern Arapahoe…eastern Douglas and western Elbert counties. The hail ranged from 1 inch to 3 inches in diameter. The largest hail was observed near Elizabeth. Areas in and around Aurora…Byers…Parker and Thornton were also impacted by large hail. One weak tornado touched down near prospect valley but did no damage. At Denver International Airport…a peak wind gust to 35 mph was observed from the northwest.


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 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 golfballs 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.

» Click here to read the rest of June 10 to June 16: This week in Denver weather history

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