Above normal temps, only a slight chance for a storm for Thornton’s Wednesday

Today we return to conditions we have seen way too much of – above normal temps, dry conditions. Mercury readings will be a good bit above average and we only have the slightest of chances for precipitation today.

Mostly sunny skies start us off and will be with us most of the day. The mid-afternoon will bring a few more clouds. High temperatures will be topping out near the 90 degree mark, about 5 degrees above average.

This evening, we may see some isolated thunderstorms but these will likely yield little more than wind and virga. Those will wrap up by late evening then skies will begin to clear. Overnight lows will dip to around 60 degrees.

Thornton’s September 2026 preview: Usually one of the most pleasant months of the year

Thornton's September weather preview.
Thornton’s September weather preview.

Following a summer that was unseasonably warm and dry, we find ourselves heading into September hoping for relief.  The month can bring plenty of rain and even our first snow of the season but more often than not, it is one of the most pleasant along the Colorado Front Range.

As temperatures start to drop, September usually reminds us that summer is at an end and fall is now here. Sunshine is predominant though as the month actually has the highest percentage of sun out of any month. Sunny days and clear, cool nights are the standard weather pattern for the month.

The month can bring extremes however.  We will of course forever remember 2013’s devastating floods brought on by record-setting rain.  Longtime residents might remember September 1971 which brought over 17 inches of snowfall.

Get a complete look at September’s weather and more details as to what we can expect this year here.

August 30 to September 5: This week in Denver weather history

This Week in Denver Weather History

As always, when looking at weather history we are reminded of the varied and sometimes dangerous weather conditions we have here in Colorado.  Our look this week we see high temperatures soaring to 97 degrees but also we see the earliest snowfall on record.

From the National Weather Service:

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.

30

In 1981…60 mph winds were reported in Boulder.

In 2004…a severe thunderstorm produced hail as large as 1 inch in diameter in south Aurora near Cherry Creek.

In 2016…an intense thunderstorm produced very heavy rain and hail in Westminster…where radar estimated up to 3.6 inches of rainfall. Several vehicles were stranded in 2 to 3 feet of moving water at the intersection of 72nd Ave. and Pecos St. Street flooding was also reported on U.S. 36 at Pecos St.

31

In 1951…hail as large as 1 3/4 inches in diameter caused an estimated 300 thousand dollars damage in metro Denver. Hail as large as 1 1/2 inches in diameter was measured at Stapleton Airport.

In 1978…strong thunderstorm winds tore the roof off an apartment building in Aurora…downed trees…and damaged windows in Denver.  A microburst wind gust to 58 mph was recorded at Stapleton International Airport.

In 1985…a thunderstorm wind gust to 60 mph was clocked at Buckley Field in Aurora.

In 1997…hail to 1 1/4 inches in diameter was measured in Aurora.

In 2006…a female postal worker was struck and injured by lightning while delivering mail in Westminster.

In 2008…lightning struck a home in Brighton…damaging the roof and a bedroom.  The damaged totaled 20 thousand dollars.

In 2020…a worsening drought that started in the spring of 2020…continued through August. The month of August tied with 2011 for the warmest August on record. It also occurred in the middle of the second warmest summer on record. The combination of hot and dry conditions…in addition to critically dry fuels from years of beetle kill…resulted massive wildfires. The Cameron Peak fire…which became the largest wildfire in the state`s history started on August 13th and continued to burn into October. Smoke from this wildfire in addition to several other large wildfires in Colorado and the West resulted in multiple days of extremely poor air quality. In addition…the air quality in Denver and the entire Front Range had deteriorated severely due to the very warm temperatures and high ozone content… which had spiked significantly. In August…26 days in the month equaled or exceeded 90 degrees.

1

In 1951…large hail pounded Boulder…causing thousands of dollars in damage to roofs and automobiles.  Heavy thunderstorm rainfall flooded basements and produced widespread street flooding.

In 1966…severe thunderstorms caused local flooding in areas from Denver to the north and east.  There was scattered damage from hail and lightning.  Streets were flooded in Boulder…and streets and basements were flooded in several areas of metro Denver.  The public reported 1 inch diameter hail in Aurora and near Cheery Creek Reservoir. Thunderstorm rainfall totaled only 0.39 inch at Stapleton International Airport.

In 1985…severe thunderstorms dumped heavy rain and hail at many locations along the Front Range from Denver south. The southern and eastern suburbs of metro Denver were especially hard hit.  Rainfall from 1 1/2 to 3 inches caused extensive street flooding in Aurora where two creeks rose out of their banks.  Two homes in the city suffered minor lightning damage.  Almost 4 inches of rain fell in the Parker area.  Hail up to ping-pong ball size piled up to a foot deep and closed a road in Evergreen. Hail as large as 1 3/4 inches in diameter was reported 8 miles northeast of Deckers.  Wind gusts to 65 mph were estimated in southeast Aurora.

In 1990…marble size hail piled up to 2 inches deep in the foothills community of Kittredge…18 miles southwest of Denver.  As much as half an inch of rain fell in just 15 minutes and caused minor road and small stream flooding. A thunderstorm dropped pea to marble size hail and brief heavy rain near ward road and 64th avenue in Arvada. Minor street and small stream flooding was reported in the area.

In 1995…a strong thunderstorm microburst with only a few drops of rain produced a recorded wind gust to 85 mph at the site of the former Stapleton International Airport. The wind gust occurred at 8:30 pm MDT.  The all-time highest recorded temperature in September…97 degrees… Occurred.  The same temperature also occurred on September 5…1899…September 4…1960…and September 4… 1995.

In 2019…the high temperature in Denver reached 98 degrees… which not only broke the record for the date…but also set a new monthly record for the month of September.

1-5

In 1995…record breaking heat occurred on the first 5 days of the month when the temperature climbed into the 90’s on each day.  Record high temperatures of 97 degrees on both the 1st and 4th equaled the all-time record maximum for the month.  High temperature of 95 degrees on the 3rd was a record for the date.  High temperatures of 94 degrees on both the 2nd and the 5th were not records.  The low temperature of 64 degrees on the 4th equaled the record high minimum for the date.

1-7

In 1978…the temperature reached 90 degrees or more on seven consecutive days with the highest temperature…94 degrees… Recorded on both the 4th and 6th.

1-30

In 2020…a worsening drought that started in the spring and continued through September. Outside of an early season snow on the 8th…the month of September was another unseasonably warm and dry period. The combination of hot…mostly dry conditions…and critically dry fuels… resulted in a continuation and rapid expansion of several massive wildfires. The Cameron Peak fire…which became the largest in the state`s history started on August 13th…and continued through September. As a result…very poor air quality continued to impact Denver and the entire Front Range. Denver recorded the most days ever with a high temperature of 90 degrees or better; 75 days. The last of which was 91 degrees on the 24th. The previous record was 73 days set in 2012.

2

In 1938…heavy cloudbursts in the foothills near the top of Genesee Mountain caused flash flooding on Bear Creek at Morrison.  Nearly 8 inches of rain fell just north of Morrison in 6 hours and drowned 6 people in a car between Morrison and Kittredge.  Damage was estimated at nearly a half million dollars.  Flash flooding also occurred on south Boulder creek in Eldorado Springs. Rainfall totaled 4.42 inches in Eldorado Springs…and rainfall was estimated to more than 6 inches in the foothills west of the town.  Many buildings and residences were damaged in Eldorado Springs…and bridges were swept away.  The high waters forced residents from their homes as far downstream as Erie.  This was the flood of record on south Boulder Creek.

In 1973…hail to 3/4 inch diameter was reported in Boulder.

In 1987…lightning struck two men who were standing under a tree in downtown Denver.  Both were seriously injured and hospitalized.

In 1996…lightning sparked a brush fire in the south buffer zone of the rocky flats environmental test facility.  No structures were damaged…but the fire burned about 100 acres of grassland before being contained.

In 2019…the record high temperature of 100 degrees was set in Denver…shattering the previous daily record of 95 established in 1983. Not only was the daily record set… it also set the all time monthly record for September. The previous record for the month was 98 degrees…which was set the previous day. In addition…it was the latest 100+ degree day ever reached during the calendar year in Denver`s climate record…breaking the previous mark by 17 days. The previous record occurred on August 16th…2002. Lastly…it was the hottest Labor Day on record.

2-3

In 1892…there was a trace of rainfall each day.  This… Together with a trace of rain on both the 7th and 8th…was the only rainfall of the month…making the month the driest on record.  The monthly record was equaled in 1944.

Continue reading August 30 to September 5: This week in Denver weather history

August 23 to August 29: This week in Denver weather history

This Week in Denver Weather History

Quite the interesting week in Denver weather history.  Swarms of grasshoppers are the most unusual item we see but there is plenty of standard severe weather including tornadoes, landspouts, hail, lightning and much more.

From the National Weather Service:

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.

22-24

In 1987…some locations in metro Denver had a total 3-day rainfall of 2 to 4 inches.  Rainfall totaled 0.96 inch at Stapleton International Airport.

23

In 1900…northwest winds were sustained to 42 mph with gusts to 49 mph.

In 1921…a thunderstorm cloudburst produced 2.20 inches of rainfall in an hour over downtown Denver.  This is the greatest 1 hour rainfall on record at the official observing site in the city.  Precipitation totaled 2.93 inches…which is the greatest calendar day precipitation ever recorded in august.

In 1941…one man was killed by lightning about 2 miles from the official weather station in downtown Denver.

In 1962…a home near Boulder was destroyed by a lightning- caused fire.

In 1968…strong winds buffeted Boulder briefly during the early morning hours.  At the National Center for Atmospheric Research…winds averaged 55 mph with gusts to 85 mph.  Damage was minor.  Northwest winds gusted to 31 mph at Stapleton International Airport.

In 1977…lightning damaged at least 6 homes in Aurora.

In 2008…a landspout touched down near Westcreek in Douglas County.  One man was seriously injured when he tried to escaped several falling trees in his ATV.  One of the trees struck his back and broke two vertebra.  Another camper narrowly escaped injury.  Seconds after he back up his truck…a tree came down where it had been parked.

In 2019…a severe thunderstorm produced large hail…up to 2 1/2 inches in diameter 5 miles west of Byers. Hail up to 1 3/4 inches in diameter was reported near Bennett.

24

In 1880…a thunderstorm produced vivid lightning and heavy rainfall…which caused flooding over the eastern part of the city including the brick yards.  There was no rainfall recorded in downtown Denver.

In 1910…an apparent dry cold front caused a remarkable drop in temperature.  From 3:00 pm until midnight the temperature fell from a high of 93 degrees to a low of 40 degrees. Northeast winds were sustained to 44 mph during the late afternoon.

In 1946…heavy rain near Idledale caused flooding on Bear Creek at Morrison…which resulted in one death when a woman was swept from her stranded car and drowned.

In 1973…strong winds blew down a few power lines and hail up to 3/4 inch diameter fell in southeast Aurora.

In 1984…heavy rain hit the south Denver area.  Over an inch fell in less than an hour at both Castle Rock and Sedalia.

In 1992…heavy rains caused flash flooding across parts of metro Denver.  Rainfall amounts of 1 to 3 inches fell with the hardest hit areas being the southwest and central parts of metro Denver.  Bear Creek rose above bankfull near Idledale with flood waters moving into southwest metro Denver.  Mud and rock slides along Colorado highway 74 west of Morrison were reported.  The confluence of Cherry Creek and the South Platte River in downtown Denver also went out of its banks…flooding bike paths.  Rainfall totaled 1.98 inches at Stapleton International Airport where light to moderate rain fell most of the day.  Heavy rain and fog briefly reduced the surface visibility to 1 1/2 miles.  The temperature climbed to a high of only 58 degrees…which was a record low maximum for the date.

In 2002…hail to 7/8 inch in diameter was measured in southwest Denver.

In 2008…several landspout tornadoes developed along a boundary to the southeast of the Denver metropolitan area during the democratic national convention.  In northwest Elbert County… Minor damage was reported.  The damage consisted of downed power lines…broken windows and an out building.  Severe thunderstorms also produced very heavy rain and large hail… Up to one inch in diameter.  In southwest Douglas County… Heavy rain caused flash flooding near the town of Westcreek. A mudslide closed State Highway 67.  The road in the YMCA camp shady brook was also washed out and some bridges were damaged.

24-26

In 1910…the lowest temperature ever recorded in August…40 degrees…occurred on each of these days and on August 22… 1904.  The unusually cold weather for so early in the season brought sub-freezing minimum temperatures to much of the Colorado northeastern plains.

25

In 1951…a microburst produced a southwest wind gust to 50 mph at Stapleton Airport.  Only a trace of rain was observed.

In 1964…thunderstorm winds gusted to 59 mph and caused some blowing dust at Stapleton International Airport.

In 1994…lightning struck a power pole in Louisville and caused a two-hour power outage.

In 2008…an unoccupied home was struck by lightning in Aurora… Causing 75 thousand dollars in damage to the roof.

26

In 1944…one of the most destructive hailstorms in the city in a decade caused damage estimated at nearly one million dollars.  The storm occurred within a period of 10 to 30 minutes…between 2:00 pm and 3:00 pm.  The hail varied in size from very small to as large as 1 1/2 inches in diameter.  Hail covered the ground to a depth of 5 to 6 inches in some sections of the city.  Several people were cut by broken glass.  The hail and heavy rain flooded underpasses to a depth of 6 feet…and the occupants of stalled autos had to be rescued.  Sewers were unable to handle the sudden amount of water and water backed up and flooded a number of basements.  A few first floors of buildings were flooded.  The water department had a busy time replacing manhole covers that had been displaced by the water pressure.  Trees were stripped…one was severely broken…and telephone lines were downed.  Roofs…windows… Automobiles…awnings…and gardens were severely damaged. Flowers and gardens in some sections of the city were a total loss.  Greenhouses were extensively broken with an estimated 20 carloads of glass shattered.  Vegetable and truck crops in and around the city were severely shredded. The next day the American Red Cross was designated by the War Agency to grant any and all priorities needed to obtain materials and supplies to replace and repair the damage. In downtown Denver…the thunderstorm produced 0.95 inch of rain and heavy hail along with sustained northwest winds to 25 mph.

In 1961…strong winds blew in the walls of a warehouse under construction in Denver.  Two workmen suffered a fractured foot and body bruises.

In 2014…two men in central Denver were struck by lightning as they sat under a tree to avoid a heavy downpour. One of the men was unconscious and had no pulse when emergency responders arrived. He was immediately taken to Denver Health was listed in critical condition. The other victim suffered less severe injuries. He was treated at the scene and hospitalized…then released a few hours later.

26-27

In 1980…two heavy thunderstorms hit Arvada and Westminster… Dumping up to 1.50 inches of rain in less than an hour. At least two streets were washed out and a number of homes and cars were damaged when a creek flooded.  Three homes in Arvada sustained minor lightning damage.

27

In 1910…a thunderstorm produced south winds sustained to 40 mph.

In 1961…strong thunderstorm winds and heavy rain occurred at 79th and Federal Blvd. In Westminster.  The strong winds blew the roofs off lumber sheds onto parked cars.

In 1967…a young woman was killed by lightning while horseback riding in the suburbs just west of Denver.  Her horse died several hours after the incident.  A young man and another young woman were also knocked from their horses by the impact of the lightning and required hospitalization.

In 1991…heavy thunderstorm rainfall totaled 0.91 inch at Stapleton International Airport…where 1/4 inch diameter hail was measured.

In 1996…localized street flooding occurred in the Fort Lupton area when 2 to 3 inches of rain fell in 45 minutes. The roof of a community college began leaking…which caused damage to ceiling tiles.  The roof was under repair from hail damage which had occurred earlier in the summer.  A weak tornado (f0) was sighted near Fort Lupton.  No damage was reported.

In 1999…a slow moving thunderstorm dumped 5 inches of rain in 2 hours near Dacono.  A severe thunderstorm produced 3/4 inch diameter hail in Castle Rock.

In 2002…severe thunderstorms spread large hail over metro Denver.  Hail as large as 2 inches in diameter fell in Jefferson County 5 to 11 miles northwest of Golden.  Other large hail reports included:  1 1/2 inches near Golden and in Lakewood; 1 1/4 inches in Nederland; 1 inch hail near Elizabeth…Louviers…Rollinsville…and Blackhawk; 7/8 inch hail near Acequia in Douglas County.  A thunderstorm produced a trace of rain and a microburst wind gust to 52 mph at Denver International Airport.

In 2003…lightning struck a house and sparked a fire in Arvada.  Damage to the roof and ceiling was extensive.

In 2005…lightning struck an unoccupied home in Parker. The resulting fire damaged the roof…attic…and second floor bedroom.  Damage was estimated at 15 thousand dollars.

27-28

In 2004…a brief chilly spell resulted in three temperature records.  The high temperature of 55 degrees on the 27th was a record low maximum for the date.  The low temperature of 48 degrees on the 27th equaled the record minimum for the date.  The low temperature of 42 degrees on the 28th was a record minimum for the date.

28

In 1887…a dry thunderstorm produced north winds to 48 mph but only a trace of rainfall.

In 1968…one man was seriously injured by lightning while riding on a roller coaster at a Denver amusement park.  An airline employee was injured when lightning struck a jetliner he was servicing at Stapleton International Airport.  A lightning-caused fire did extensive damage to one house and minor damage to several others in the city of Denver.

In 1970…a microburst wind gust to 53 mph was recorded at Stapleton International Airport.

In 2002…a severe thunderstorm produced 3/4 inch diameter hail near Parker.

In 2005…lightning sparked a small fire near Jamestown.  The blaze was quickly contained and consumed less than an acre.

In 2022…a thunderstorm produced a peak wind gust to 53 mph at Denver International Airport from the south-southwest. Just a trace of rainfall was observed.

29

In 1876…after the passage of a gentle rain shower to the east during the late evening hours…the moon shone brightly and a remarkably bright lunar rainbow appeared.

In 1910…an apparent cold front produced sustained northeast winds to 40 mph.

In 1946…the high temperature warmed to only 55 degrees…the record low maximum for the month.

In 1989…a spectacular lightning display knocked out power to 300 blocks in southeast Denver.  One bolt started a fire in a lumber yard in the northeast part of the city…and the attic of a home in the same area was set ablaze by a lightning bolt.

In 1996…3/4 inch diameter hail was measured in Parker.

In 2000…lightning struck two homes in Thornton.  The extent of damage was unknown.

In 2002…two small tornadoes caused damage in southeast metro Denver.  The first tornado…associated with a multi-vortex storm…touched down briefly near E-470 and South Jordan Road.  Some fences were damaged…and a few trees were blown down.  A few of the homes also sustained minor roof damage. Damage from this storm totaled 100 thousand dollars.  The second tornado associated with the storm touched down in a subdivision that was under construction at Gartrell and Arapahoe roads.  Four large condominiums under construction were destroyed.  The most heavily damaged portions of the structures were still in the framing stages.  Adjacent sections where enclosed walls were in place were not destroyed.  A man suffered 4 broken ribs and several cuts and bruises when the trailer he sought shelter in was flipped three times and torn apart by the twister.  Damage from this storm totaled 6 million dollars. A severe thunderstorm produced 1 inch diameter hail near Evergreen.

In 2006…severe thunderstorms produced large hail in the foothills west of Denver.  Hail to 1 inch in diameter fell near Blackhawk.  Hail as large as 7/8 inch was measured near Idaho Springs…along with 3/4 inch hail near Nederland and Conifer.

NOAA fall outlook indicates a mild, potentially damp, fall for Colorado

NOAA Fall 2026 Outlook for Temperatures. (NOAA)
NOAA Fall 2026 Outlook for Temperatures. (NOAA)

The National Oceanic and Atmospheric Administration’s (NOAA) Climate Prediction Center (CPC) has released its three-month outlook for the upcoming meteorological fall that begins in less than two weeks. In it, the agency indicates Colorado will see continued mild temperatures but also increased chances for precipitation.

For temperatures, the agency gives most of Colorado a 33 to 40% chance of seeing above average temperatures. This would, unfortunately, continue with what we have experienced thus far this year.

In terms of precipitation, things do look a bit better. The three-month outlook indicates a 40 to 50% chance of above average levels for most of Colorado. Some areas north and east have a 33 to 40% chance.

There has been talk about an unusually strong El Niño developing that will impact the Northern Hemisphere. Its effects on Colorado, however, are less than clear. We are far inland and largely removed from ocean impacts.

However, El Niño does oftentimes result in greater than average snowfall for the southern and southwestern parts of the state. Further north, its effects are less predictable and we are more dependent on individual storms and the track they take.

NOAA Fall 2026 Outlook for Precipitation. (NOAA)
NOAA Fall 2026 Outlook for Precipitation. (NOAA)

August 16 to August 22: This week in Denver weather history

This Week in Denver Weather History

August is usually considered one of the calmer weather months in Denver but as our look back in weather history for this week shows, that isn’t always the case.  Thunderstorms and all their associated dangers – lightning, flooding, tornadoes and more – all present a very real danger even this time of year.

From the National Weather Service:

16

In 1902…a thunderstorm produced west winds sustained to 48 mph with gusts to 60 mph…but only a trace of rain.

In 1952…a thunderstorm wind gust to 50 mph was recorded at Stapleton Airport.

In 1960…lightning struck a warehouse in central Denver… Causing 8 thousand dollars in damage to the building and stored electrical equipment.

In 1975…large hail…1 1/2 to 1 3/4 inches in diameter…fell about 4 miles north of Castle Rock.  Hail caused some minor damage in Aurora.  A funnel cloud was reported 25 miles east of Denver near Bennett.

In 1981…a tornado touched down briefly in open country just to the east of Aurora.  No damage was reported.

In 1982…a thunderstorm wind gust to 61 mph was recorded at Buckley Field in Aurora.  At the same time almost an inch of rain flooded and closed streets in south Aurora.  A women was hit by lightning just north of Denver.  A house in the area was also struck.

In 1985…a thunderstorm produced strong wind gusts over southern metro Denver.  One strong wind gust hit Cheery Creek Reservoir…capsizing a boat and drowning a man.  The wind gusts…clocked as high as 50 mph…also downed a few trees.

In 1989…1 3/4 inch diameter hail fell at Intercanyon in the foothills of Jefferson County.

In 1990…lightning caused minor damage to a south Aurora home.  No injuries were reported.

In 1994…strong thunderstorm winds caused damage in southern Weld County near Hudson and Fort Lupton.  Two mobile homes were destroyed and a few lost their roofs.  Up to 20 downed power poles and the destruction of two 115 thousand-volt towers caused widespread power outages.  Thunderstorm gust front winds from the north gusted to 48 mph at Stapleton International Airport.

In 2000…lightning ripped most of the roof from a home in southeast Aurora.  The bolt sparked a fire which destroyed the residence.  Damage was estimated at 250 thousand dollars.

In 2002…the temperature climbed to a maximum of 100 degrees setting a new record high for the date.

In 2003…a teenager was injured when he was struck by lightning while camping at Herman Lake…13 miles northwest of Georgetown.  The boy was knocked unconscious and suffered minor injuries.

In 2022…heavy rainfall produced extensive flooding in Broomfield. Six inches of water inundated a section of Highway 287. Bike paths were flooded along Rock Creek and near Spader Way near the Broomfield Events Center. Spader Way was closed due to flash flooding from 1st Avenue to DesCombes Drive. Storm totals up to 3.62 inches observed in the area. Bike paths flooded with several feet of water along Coal Creek in Lafayette and Rock Creek.

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.

17

In 1953…a tornado was sighted 8 miles east of Castle Rock. An unconfirmed tornado was sighted between Denver and Strasburg.  No damage was reported.

In 1963…heavy rain in southeast Denver…Englewood…and Littleton caused flooding of basements and streets.  Over 3.00 inches of rain fell at Cherry Creek Dam.  Lightning caused power failures.  The hardest hit areas were in north- central Denver.  A 12-year-old boy was swept into a conduit by a 3-foot high crest of water.  He was carried 125 feet through the waterway…but was unhurt.  Thunderstorm rainfall totaled only 0.24 inch at Stapleton Airport.

In 1972…a thunderstorm wind gust to 53 mph was recorded at Stapleton International Airport.  Strong winds also occurred in the Littleton area where several trees and utility poles were blown over and a number of windows broken.

In 1978…1 3/4 inch diameter hail was reported in Thornton.

In 1982…heavy rain occurred in the foothills southwest of Denver where 4.50 inches fell in 75 minutes between Evergreen and Conifer.  Nearby…2.66 inches of rain drenched the North Turkey Creek Canyon area in just 15 minutes.

In 1984…scattered slow moving thunderstorms dumped heavy rain across southern metro Denver.  The heavy rain caused some road washouts in Jefferson and Douglas counties.  A bridge was washed out in Douglas County.  Three inches of rain fell in just an hour at Castle Rock…causing heavy silt damage to a home and to nearby drainage ditches.

In 1988…a thunderstorm dumped 2 to 3 inches of rain in southeast Denver and adjacent areas of Arapahoe County in less than 90 minutes.  There was widespread street flooding…and I-25 was closed by 4 feet of water near its intersection with I-225 just south of Denver.  A flood control project in Arapahoe County at greenwood village sustained over 10 thousand dollars damage.  Up to 4 feet of water flooded some basements in the area.  Only 0.44 inch of rain fell at Stapleton International Airport.

In 1990…heavy thunderstorm rains over the Boulder creek and St. Vrain creek drainage basins caused many creeks and drainage ditches to rise in eastern Boulder and southwest Weld counties.  The high waters punched three 30-foot holes in the embankment of a drainage ditch…which traversed through the town of firestone…20 miles north of Denver. A sheet of water 2 to 3 feet deep rushed out onto the streets of firestone…forcing the evacuation of a trailer park and residents from 50 neighboring homes.  No injuries or serious damage occurred except for mud and water damage. Lightning struck and injured 4 construction workers standing in an Aurora field.  They received treatment for minor injuries at a local hospital.  Lightning also struck the roof of a Methodist church in central Denver… Knocking down the highest peak of the steeple.  A half dozen people were in the building…but no one was injured. Slow moving thunderstorms dumped 2 to 3 inches of rain over southeast Aurora in 90 minutes.  The heavy rain accumulated on the roof of a condominium clubhouse…causing the roof to collapse under the weight of the water.  Nearly 300 residents were evacuated from the 200-unit complex because of the structural damage.  The residents were allowed to return to their homes when it was determined the damage was confined to the clubhouse.  No injuries were reported.

In 1993…just west of Fort Lupton…thunderstorm winds blew the tin roof off a cattle shelter into a mobile home… Causing considerable damage to the mobile home.

In 1997…lightning struck a home in Castle Rock sparking a fire.  Damage was estimated at 20 thousand dollars.

In 2000…thunderstorms producing very heavy rain…up to 3.50 inches in spots…caused flooding and flash flooding across metro Denver.  In Commerce City…a 37-year-old firefighter drowned while attempting to rescue a stranded motorist on a flooded street.  The firefighter was wading through the water when he lost his footing and was sucked into a 10 foot deep culvert.  He was swept away before anyone could reach him.  Extensive flooding was also reported throughout Littleton and north Denver.

18 Continue reading August 16 to August 22: This week in Denver weather history

August 9 to August 15: This week in Denver weather history

This Week in Denver Weather History

Denver and Colorado as a whole are known for their unusual weather.  This week in particular is notable for one extraordinary event in weather history – clouds of grasshoppers!

8-10

In 1979…heavy thunderstorm rains on each of three consecutive days dumped a total of 2.22 inches of rain at Stapleton International Airport.  The heaviest rain… 0.95 inches…fell on the 9th.  Small hail to 1/8 inch diameter fell on the 8th.

8-13

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

9

In 1900…a thunderstorm produced west winds sustained to 47 mph with gusts to 55 mph…but only 0.01 inch of rain.

In 1902…a thunderstorm produced no rain and north winds sustained to 52 mph with gusts to 60 mph.

In 1934…heavy cloudbursts in the foothills near Kittredge and at the head of Mount Vernon creek caused flash flooding on both bear creek and Mount Vernon Creek at Morrison… Which resulted in 6 deaths and much property damage. The highway in Mount Vernon Canyon was destroyed by the flood waters.

In 1981…3/4 inch hail fell at Kittredge near Evergreen in Jefferson County.

In 1987…3/4 inch hail fell in Boulder and 9 miles northwest of Castle Rock.

In 1995…lightning struck a 16-year-old counselor in the back of the head while he and a friend were standing under a tree at the singing river ranch…7 miles west of Evergreen.  He stopped breathing…but his friend was able to summon help and they were able to revive him.  He was hospitalized for a few days and released.

In 1998…brief…weak tornadoes (f0) were sighted near Bennett and Roggen.  No damage was reported.  Hail as large as 1 inch diameter fell in Franktown with 3/4 inch diameter hail measured near Castle Rock. Thunderstorm winds gusted to 61 mph near Roggen.

9-10

In 2006…mid and high cloudiness overnight on both days resulted in two temperature records.  The low temperature of 71 degrees on the 9th was a record high minimum for the date.  The low temperature of 68 degrees on the 10th equaled the record high minimum for the date first set in 1936.

10

In 1924…0.01 inch of rain fell over downtown Denver.  This along with the 0.01 inch of rainfall on the 4th was the only rainfall of the month…making this the driest august on record in the city.

In 1962…the high temperature reached 100 degrees at Stapleton Airport.

In 1970…hail stones to 1 inch in diameter were reported in the Fort Lupton area.

In 1972…dry thunderstorm microburst winds gusting to 46 mph briefly reduced the surface visibility to 3/4 mile in blowing dust at Stapleton International Airport.

In 1978…lightning struck two men in Aurora…killing one and injuring the other.

In 1982…a tornado was sighted near Castle Rock and remained on the ground for 10 minutes.  Wind gusts to 60 mph were reported in Castle Rock.  No damage was reported.

In 1994…heavy thunderstorm rains caused flash flooding on Lena Gulch in west metro Denver.  Damage was estimated at 50 thousand dollars.  Lightning struck a house in Westminster…causing a small attic fire.

In 1996…strong thunderstorm winds toppled a tent at a company picnic in Westminster.  Five people received minor injuries when the tent collapsed.  Two cars nearby were also damaged by flying debris.  A weak tornado (f0)…first sighted near Denver International Airport…traveled east to near Bennett and Strasburg.  No significant damage was reported.

In 1998…heavy rain caused flooding and flash flooding problems over southwest metro Denver.  An observer in Lakewood measured 3.26 inches of rainfall in an hour. Several streets were flooded in central Lakewood.  In addition…a trailer park along Lena Gulch in Wheat Ridge was evacuated due to high waters.  One inch diameter hail fell near Roggen.

In 1999…thunderstorm-producing tornadoes…damaging straight line winds…heavy rain…and hail hammered metro Denver.  In the city…small hail and heavy rainfall…up to 2.50 inches an hour…caused a 20-foot by 50-foot section of the roof to collapse at a furniture warehouse.  Damage to the warehouse was estimated at 1 million dollars.  Heavy rain also flooded several underpasses with up to 3 feet of water…which resulted in a number of stalled vehicles.  In Fort Lupton…a tornado bounced across the area.  Spotty damage was reported along a 5-mile path as trees…power poles…and lines were downed.  In addition…an empty semi-trailer was overturned onto another vehicle northeast of the town.  Thunderstorm winds gusted to 81 mph south of Fort Lupton.

In 2004…severe thunderstorms pummeled metro Denver with large hail.  Hail up to 3 inches in diameter was measured 10 miles east of Castle Rock.  Two inch diameter hail fell in Louisville…10 miles north of Hudson…and 1 mile east of Brighton.  Hail to 1.75 inches was reported in Englewood… 1 mile south of Ft. Lupton…and 8 miles east of Boulder. Hail to 1.50 inches was reported around Boulder…near Broomfield…and in Lafayette…Thornton and greenwood village. Hail from 3/4 to 1 inch in diameter was found in Broomfield… Brighton…Castle Rock…Denver and Thornton…and near Longmont… Northglenn…Greenwood Village…Morrison…and Wheat Ridge. Severe thunderstorm wind gusts were recorded to 66 mph in Parker and to 60 mph 5 miles northeast of Boulder.  There were no damage estimates from the hail or wind.

Continue reading August 9 to August 15: This week in Denver weather history

Denver breaks record low temperature for August 5

Record Cold Temperatures

Did you feel a very slight chill in the air this morning? It was very pleasantly cool and in fact, record-tying.

As measured at Denver International Airport, the city’s official low temperature dipped to 47 degrees. This breaks the record low for the date set in 1978.

Amusingly enough, the record low follows record-setting heat. Just two days ago, Denver set a record high temperature.

Here in Thornton, we weren’t quite as cool with a low of 50 degrees. That was our coldest August 5th reading in the past 20 years that Thornton Weather has been operating. The previous low for the date was 53.9 degrees in 2015.

Editor’s note: This story originally reported Denver’s low as 48 degrees, per the National Weather Service. They then revised the number to 47 degrees and the story was updated accordingly.

Thornton’s August 2026 preview: Temps begin to cool, severe weather eases

Thornton's August Weather Preview
Thornton’s August Weather Preview

As summer vacations wind down and families prepare to send their kids back to school in August, Colorado weather also starts to settle down. The chances for severe weather decrease markedly during August and by the end of the month daytime temperatures are dropping quite a bit as well.

Find out more about what lies ahead with Thornton’s August weather here.

Denver sets high temperature record for August 3

Record High Temperature

The heat has been on throughout the summer and continued today as Denver set another record high.

As measured at Denver International Airport, the Mile High City’s official high temperature today came in at 102 degrees. That breaks the old record high for the date of 100 degrees set in 1878.

Here in Thornton, we bested Denver slightly with a high of 103 degrees.

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