Thornton, Colorado, USA
UpdatedSun, 02-Oct-2022 7:40am MDT 


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Fall arrives Thursday in Thornton with season-appropriate weather conditions

Thursday, September 22nd, 2022 5:09am MDT

The autumn equinox is here with fall officially arriving at 7:03pm and Mother Nature saw fit to deliver weather conditions appropriate for the new season. Following on yesterday’s cool, damp day, we see somewhat similar conditions today although drier air is beginning to filter in so rainfall will lessen.

Cloudy skies start us off and will be with us most of the day. By mid-afternoon the coverage should start to ease up and we may see some patchy blue. Light rain showers will be possible through the day, perhaps with some thunder in the late afternoon and early evening. High temperatures will top out in the low to mid-60s.

Tonight, any showers will end early and skies will begin to clear. Look for overnight lows around 50 degrees.

Our live radar will keep you up to date on the showers.

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Wednesday brings much cooler temperatures, good chances for rain

Wednesday, September 21st, 2022 6:00am MDT

Our much-anticipated cool down has arrived. With the passage of a cold front Thornton will see a 30+ degree temperature difference today versus yesterday and we will see some welcome precipitation.

Cloudy skies greet us at dawn and will be with us throughout the day. Our warmest temperature readings will actually be seen early with daytime highs around 60 degrees. The mercury will then actually cool a few degrees as the day progresses. A few sprinkles of rain may be seen this morning then chances increase with some light showers expected in the afternoon.

Chances for rain increase in the evening and through the overnight hours when a healthy dose is expected. Showers will then ease after midnight with precipitation becoming lighter. Overnight lows will be in the low to mid-50s.

Keep an eye on current conditions including rain totals with our live gauges here.

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Tuesday to bring one more hot day to Thornton before things cool down

Tuesday, September 20th, 2022 4:57am MDT

Yup, another hot one for us today but a taste of fall lies in waiting and it will quite possibly be the last 90 degree day of the year.

Overall, today’s daytime weather looks much like yesterday’s. We will enjoy sunny skies for the majority of it then see some clouds in the mid to late afternoon. Highs will top out in the low 90s with dry, overall calm conditions.

Tonight, we begin to see a change. A cold front will push through and as it does, winds and cloud cover will increase. Some sprinkles / light rain will be possible after 9:00pm and then through sunrise tomorrow. Overnight lows will dip to the mid-50s.

Looking ahead, Wednesday and Thursday offer up considerably cooler weather with decent chances to receive some precipitation. Have a look at the extended forecast for more.

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Very warm temperatures, dry conditions start off Thornton’s workweek

Monday, September 19th, 2022 4:56am MDT

We have a few more days of summer and Mother Nature is going to remind us of that on two of those with well-above normal temps.

For today, we start out with sunny skies then will see some clouds in the afternoon and evening. High temperatures are going to push to highs near the 90 degree mark. Overall, conditions will be calm and dry.

Tonight, it will be partly cloudy initially then clearing after midnight. Overnight lows will dip to the mid to upper 50s.

We’ll have one more very warm day tomorrow then see a break and a taste of fall for Wednesday and Thursday.

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

Sunday, September 18th, 2022 5:13am MDT

This Week in Denver Weather History

The calendar may still say it is summer for a few more days but our look back at this week in Denver weather history shows that Old Man Winter can still make an appearance.

From the National Weather Service:


In 2018…the high temperature equalled or exceeded 90 degrees for 9 consecutive days; marking the first time such an occurrence has taken place in the month of September. It also brought September of 2018 into a 4-way tie for most 90 degree + days in the month. Previous years included 2017…2005 and 1895. During the streak…4 record high temperatures were either tied or broken…and one record high minumum temperatures was broken.


In 1906…rain on 5 consecutive days totaled 1.61 inches. A thunderstorm occurred on the 17th. High temperatures ranged from 48 degrees on the 16th to 65 degrees on the 15th. Low temperatures were in the lower to mid 40’s.


In 1971…a record breaking early fall snow storm caused extensive damage to trees and utility lines. The heavy wet snow occurred with little wind…but caused record breaking cold temperatures for so early in the season. Snowfall totaled 15.6 inches at Stapleton International Airport with most of the snowfall…12.0 inches…occurring on the 17th. This was the heaviest first snow of the season. The maximum snow depth on the ground was 13 inches. Record low temperatures were set on three consecutive days: 31 degrees on the 17th…23 degrees on the 18th…and 20 degrees on the 19th…which was also a new all-time record minimum for the month at that time. Record low maximum temperatures were set on 4 consecutive days: 48 degrees on the 16th…35 degrees on the 17th…40 degrees on the 18th… And 42 degrees on the 19th.


In 1901…northeast winds were sustained to 42 mph with gusts to 50 mph behind an apparent cold front.

In 1948…the low temperature cooled to only 69 degrees…the all-time record high minimum for the month.

In 1988…a strong cold front blasted metro Denver with high winds. Gusts reached 82 mph in Longmont and 81 mph at Jefferson County Airport near Broomfield where the winds flipped over and destroyed a small airplane. Wind gusts to 60 mph were recorded in Boulder and Wheat Ridge. West wind gusts to 54 mph were clocked at Stapleton International Airport. The strong winds downed trees and power lines and damaged homes and cars. A Longmont man was slightly injured…when a tree fell on top of his car.

In 1990…a slow moving thunderstorm over southwest metro Denver spawned an ominous looking funnel cloud near the intersection of Sheridan Blvd. and U.S. Highway 285. The funnel cloud nearly touched down a few times before lifting back into the main cloud. No damage was reported. Pea to marble size hail and 3/4 inch of rain fell over central and northeast Denver. Numerous streets and underpasses became flooded on Denver’s south side when the heavy runoff backed up storm sewers. Thunderstorm rainfall totaled 1.02 inches at Stapleton International Airport.

In 1993…a severe thunderstorm rolled through southeast metro Denver. Dime size hail was reported in many areas. Straight-line winds from the thunderstorm…measured by a weather spotter at 70 mph…tore the roof off 6 apartments of an apartment complex in Aurora. Heavy rain which accompanied the winds caused major damage to the apartments as well as the contents. Many trees…fences… And power poles were knocked down by the strong winds. Heavy rain flooded roadways in Denver and Aurora. Thunderstorm rainfall totaled 1.08 inches and north winds gusted to 44 mph at Stapleton International Airport where the visibility was briefly reduced to as low as 1/4 mile in heavy rain.

In 1996…a late summer snowstorm struck the northern mountains and Front Range eastern foothills. Golden Gate Canyon received 6 inches of new snow with 5 inches reported at both Nederland and Blackhawk. Thunderstorms produced heavy rain across metro Denver…which was mixed with snow by late evening. Rainfall totaled 0.83 inch at the site of the former Stapleton International Airport and 1.22 inches at Denver International Airport where northwest winds gusted to 39 mph.


In 1955…heavy rains caused flash flooding across portions of metro Denver. Rainfall totaled 1.71 inches at Stapleton Airport.


In 1955…hail stones to 2 1/2 inches in diameter were reported north of Denver. The large stones broke many automobile windshields.

In 1963…hail to 3/4 inch in diameter fell in Westminster.

In 1983…an unusually strong cold front roared through metro Denver during the afternoon hours. At Stapleton International Airport…the temperature dropped 51 degrees… From a sunny 86 degrees to a snowy 35 degrees…in just 7 hours. Strong winds and a wall of blowing dust followed the front. Northeast winds gusting to 36 mph briefly reduced the surface visibility to 1 mile in blowing dust at Stapleton International Airport where only a trace of snow fell later.

In 1996…high winds gusting to 84 mph were measured at Golden Gate Canyon in the foothills west of Denver. West winds gusted to only 25 mph at Denver International Airport.


In 1921…an apparent Bora produced northwest winds sustained to 44 mph with gusts to 64 mph.

In 1955…hail stones 1/2 to 3/4 inch in diameter were reported across parts of the city of Denver.

In 1992…weather observers at Buckley Air National Guard base sighted two tornados southeast of the base. The tornados were short-lived and caused no injuries or damage.


In 1963…heavy rain and hail caused local flooding in southeast Denver. Thunderstorm rainfall was only 0.60 inch at Stapleton Airport on the 20th.

In 1983…the cold front on the 19th brought an unusually cold air mass into metro Denver for so early in the season. The temperature dipped to a daily record minimum of 28 degrees on both days.

In 1995…a vigorous late summer storm brought the season’s first heavy snow to portions of metro Denver. Millions of trees were damaged and power lines downed as 4 to 8 inches of heavy wet snow settled on fully leafed trees in the Boulder and Denver areas. Branches snapped and trees split under the weight of heavy snow…downing power lines. Firefighters responded to numerous transformer fires. Around 100 thousand people were left without electricity in Boulder and Denver areas alone. It took over a week to fully restore power to some areas. Insurance claims were estimated to be around 6 million dollars to homes in metro Denver and about 500 thousand dollars in damage to automobiles. It was estimated that about 80 percent of 125 million dollars worth of city owned trees in Denver were damaged. Snowfall totaled 7.4 inches at the site of the former Stapleton International Airport where the greatest depth of snow on the ground was only 4 inches due to melting. Temperature records were set on the 21st when the thermometer dipped to a record low reading of 27 degrees and climbed to a high of only 36 degrees… Setting a record low maximum for the date. North winds gusted to 29 mph at Denver International Airport on the 20th. » Click here to read the rest of September 18 to September 24: This week in Denver weather history

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Thornton’s weekend to offer up pleasant, late summer weather conditions

Friday, September 16th, 2022 5:19am MDT

This forecast looks pretty good to us. Mother Nature will offer up temps near normal and pleasant conditions for this last weekend of summer.

For today, look for a good dose of sun through the morning. The afternoon will bring some clouds and a slight chance for a shower or thunderstorm. Highs will be in the low to mid-80s. Tonight, skies will clear later and overnight lows will dip to the low 50s.

Saturday brings another nice one. Mostly sunny skies will be above with highs in the low to mid-80s. There is only a slight chance for a PM storm. Saturday night, skies will be clear with lows around 50 degrees.

The weekend closes out on Sunday in fine fashion for the Broncos’ home opener with temps climbing and getting a bit toasty. Look for highs in the upper 80s under sunny skies.

Enjoy the weekend and get outside!

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Thursday will offer a cool down, another chance for thunderstorms

Thursday, September 15th, 2022 5:37am MDT

A chance to perhaps see temps end up a bit below normal in Thornton today. With the cool down, we also have a bit of a chance for afternoon thunderstorms.

Mostly sunny skies start us off, turning to partly sunny this afternoon. Late morning may bring a very light sprinkle of rain. This afternoon, a few thunderstorms may be seen but they are expected to be scattered. Hopefully some make it our way. High temperatures today will top out in the mid to upper 70s.

Tonight, a few lingering storms may be around initially. Then skies will begin to clear. Overnight lows will be in the low 50s.

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

Thursday, September 15th, 2022 5:03am MDT

This Week in Denver Weather History

Severe weather is less common as we enter the fall season but it is not entirely unheard of. As we see in our look back at this week in Denver weather history, we have seen everything ranging from torrential rains to tornadoes and even heavy snow.


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.


In 2010…the Fourmile Canyon Wildfire…northwest of Boulder… broke out on the morning of the 5th. It originated from an unattended fire pit at a local residence. The wildfire quickly consumed 5 1/2 square miles or 3500 acres the first day…and forced the evacuation of over three thousand residents. Erratic 45-mph gusts sent the fire in two directions at times. Very dry weather conditions preceded the fire. The combination of strong winds…low relative humidities and dry fuels allowed the wildfire spread rapidly through the steep…heavily forested terrain. The flames were reportedly 20 to 50 feet in length. Towns within the burn area included Salina…Wallstreet and Gold Hill. The dry conditions coupled with gusty winds ranging from 45 to 64 mph persisted for several more days. Fire managers used as many as 700 firefighters and support personnel from 35 agencies and seven air tankers to battle the wildfire. A total of 6181 square acres or approximately 10 square miles were burned. The Fourmile Canyon Wildfire was the most destructive fire in Colorado history in terms of the damage to personal property. It destroyed 171 homes with an estimated cost of 217 million dollars.


In 2018…the high temperature equalled or exceeded 90 degrees for 8 consecutive days; breaking the previous streak of 7 consecutive days in the month of September.


In 2018…the high temperature equalled or exceeded 90 degrees for 9 consecutive days; marking the first time such an occurrence has taken place in the month of September. It also brought September of 2018 into a 4-way tie for most 90 degree + days in the month. Previous years included 2017…2005 and 1895. During the streak…4 record high temperatures were either tied or broken…and one record high minumum temperatures was broken.


In 1910…west winds were sustained to 42 mph.

In 1951…a vigorous Canadian cold front produced a dust storm across metro Denver. Northeast wind gusts to 43 mph reduced the visibility at Stapleton Airport to as low as 1 1/2 miles for nearly 5 hours. The temperature dropped 47 degrees in 8 hours…from a high of 92 degrees to a low of 45 degrees.

In 1967…a microburst wind gust to 52 mph produced blowing dust and briefly reduced the visibility to 1/2 mile at Stapleton International Airport.

In 1974…a trace of snow…the first of the season…ended the shortest period without snow…94 days from June 9th through September 10th. A trace of snow also fell on June 8th.

In 1995…strong post-frontal winds associated with a fast moving pacific cold front knocked down power poles and trees as it moved through metro Denver. Numerous power outages affected nearly one thousand people in Denver and Jefferson counties. West winds gusted to 34 mph at Denver International Airport.


In 2013…a deep southerly flow over Colorado… Ahead of a nearly stationary low pressure system over the great basin… Pumped copious amounts of monsoonal moisture into the area. In addition…a weak stationary front stretched along the Front Range foothills and Palmer Divide.  This resulted in a prolonged period of moderate to heavy rain across the Front Range foothills…Palmer Divide…urban corridor. By the 14th…storm totals ranged from 6 to 18 inches… Highest in the foothills of Boulder County. The headwaters then moved down the South Platte River and caused widespread flooding with record flood stages at several locations as it made its way downstream.  The record high flood stages resulted in widespread flooding along the South Platte River basin. The flood damage encompassed 4500 square miles of the Front Range…left 7 dead… Forced thousands to evacuate…and destroyed thousands of homes and farms. Record amounts of rainfall generated flash floods that tore up roads and lines of communication… Leaving many stranded. Nearly 19000 homes were damaged… And over 1500 destroyed. Colorado department of transportation estimated at least 30 state highway bridges were destroyed and an additional 20 seriously damaged. Preliminary assessments of the state`s infrastructure showed damage of $40 million to roads and $112 million to bridges. Repair costs for state and county roads ran into the hundreds of millions of dollars. Miles of freight and passenger rail lines were washed out or submerged… Including a section servicing Amtrak`s iconic California Zephyr. The town of Lyons was isolated by the flooding of St. Vrain creek…and several earth dams along the Front Range burst or were over-topped. Floodwaters swept through Estes Park; damaged hundreds of buildings and destroyed large sections of U.S. 34 from Loveland and U.S. 36 from Lyons to Boulder. U.S. 34 suffered the most damage… With 85 percent of its roadway and bridges destroyed. In Weld County…about nearly two thousand gas wells were damaged and had to be closed off as the floodwaters inundated entire communities. Sewage treatment plants and other utilities were knocked out in a number of towns. Governor Hickenlooper declared a disaster emergency on September 13th…in 11 counties across northeast Colorado including:  Adams…Arapahoe…Broomfield…Boulder…Denver…  Jefferson…Larimer…Logan…Morgan… Washington and Weld. By the 15th…federal emergency declarations covered those counties as well as Clear Creek County. Projected losses from the flooding statewide was nearly two billion dollars in property damage…according to Eqecat… A catastrophe modeling firm.  The damage was most severe in and around Lyons and Boulder.  More than 11 thousand people were evacuated…reportedly the largest since Hurricane Katrina. President Obama declared a state of emergency for Boulder and Larimer counties.  An additional 10 counties were added on the 16th and included: Adams… Arapahoe…Broomfield…Clear Creek…Denver…Jefferson…  Morgan…Logan… Washington and Weld counties. The president also declared a major disaster specifically for Boulder County.  There were six fatalities directly attributed to flash flooding. Two 19-yr old teenagers died on the 11th…after they were swept away by floodwaters after abandoning their car on Lindon Drive in Boulder. In Jamestown…a 72-yr old man was killed when the building he was in collapsed. An 80-yr old Lyons resident died in the early morning hours of the 12th…when his truck was swept into the St. Vrain River near his home. Later on the 12th…a 79-yr old Larimer County resident was killed when she was swept away while trying to climb to safety from her home in Cedar Point. A 61-yr old cedar point resident died when her home was swept down the Big Thompson River by the floodwaters. An 80-yr old Idaho Springs resident drowned in Clear Creek when the embankment he was standing on collapsed. In Boulder…some of the monthly records broken included: one-day all-time record: 9.08 inches which shattered the previous wettest day of 4.8 inches set on July 31… 1919; one-month record of 18.16 inches…which broke the previous all-time monthly record of 9.59 inches set in May of 1995; wettest September on record which broke the previous record of 5.5 inches set in September of 1940; one-year record of 34.15 inches broke the previous wettest year of 29.93 inches set in 1995. At Denver International Airport…the total precipitation for the month of September was 5.61 inches…which was 4.65 inches above the normal of 0.96 inches. This is the most precipitation ever recorded in Denver for the month of September. Daily precipitation records included 1.11 inches on the 12th and 2.01 inches on the 14th.


In 1974…post-frontal rain changed to snow overnight for the first snow of the season. Snowfall totaled only 1.8 inches at Stapleton International Airport where north winds gusted to 40 mph on the 11th. High temperature of only 46 degrees on the 12th set a new record low maximum for the date. » Click here to read the rest of September 11 to September 17: This Week in Denver Weather History

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Cooler temperatures, a chance for thunderstorms Wednesday

Wednesday, September 14th, 2022 4:56am MDT

A weak disturbance offers up a break from the very warm temps of the last couple of days. Temps will be closer to average and the afternoon brings a chance for some thunderstorms.

The increased moisture aloft will give us a good bit of cloud cover today with partly sunny to mostly cloudy skies throughout. High temperatures will top out in the low 80s.

The afternoon sees chances for thunderstorms. The best opportunity comes from about 3:00pm to 8:00pm. Brief, heavy rain and gusty winds will be the threats from any storms that move over.

Tonight, thunderstorms will ease and be wrapped up by midnight. Skies will remain mostly cloudy. Look for lows to dip to the mid-50s.

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Tuesday in Thornton brings very warm temps, some clouds and smoke

Tuesday, September 13th, 2022 5:28am MDT

A somewhat familiar weather pattern for the day. We will see temperatures well-above normal with some cloud cover and possibly smoke once again intruding.

The day starts off sunny then we see a slow increase in cloud cover as the day progresses. Smoke will be possible for much of the mid-day. Winds will be breezy from mid-afternoon into the first part of tonight. The clouds and haze won’t do much to inhibit temperatures, however, as we still expect to see a high near the 90-degree mark.

Tonight, skies will be mostly cloudy. Winds will ease after midnight. Overnight lows will dip to below 60 degrees.

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