Thornton, Colorado, USA
UpdatedMon, 28-Nov-2022 11:45pm MST 


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

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

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 MST

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 MST

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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Lots of sun and very warm temps kick off Thornton’s workweek

Monday, September 12th, 2022 4:57am MST

Following our much needed break from the heat, we see temperatures again climb. Thankfully, however, while they will be above normal, it will be cooler than last week’s record setting marks.

Sunny skies greet us this morning and will be with us throughout the day. Temperatures start out cool early this morning but then will warm up to a high in the upper 80s. Overall, conditions will be calm and dry.

Tonight, skies will remain largely cloudless. Overnight lows will dip to the low 50s.

Enjoy the nice weather and GO BRONCOS!

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Thornton’s weekend to offer up a significant cool down, chances for showers

Friday, September 9th, 2022 6:01am MST

You asked for it and the much anticipated cool down has arrived. The weekend will offer up temperatures below normal for the first time in a long time and maybe even some rain.

For today, the day starts out with sunny skies and cool temperatures. Cloud cover will increase later this morning and this afternoon. High temps look to top out in the upper 60s. Late afternoon and evening offer a bit of a chance for a shower. Tonight, skies will become cloudy. Chances for showers increase after midnight. Overnight lows will dip to the upper 40s.

Saturday will definitely bring a taste of fall. Skies will be mostly cloudy and high temperatures will only top out near 60 degrees. Some light showers can be expected, mainly in the morning. The afternoon won’t see much in the way of precipitation and the clouds will ease some. Saturday night, any showers will end in the evening. Skies will then begin to clear and lows will drop to the mid-40s.

Sunday, Patriot Day, offers a very nice rebound and will be a nice way to close out the weekend. Sunny skies return and high temps will climb to the mid to upper 70s. Have a great weekend!

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Denver breaks two more warm weather records on September 7

Thursday, September 8th, 2022 6:57am MST

Record High Temperature

The warm weather records just seem to keep continuing to fall. Yesterday, Denver set another record high and a record low minimum.

As measured at Denver International Airport, the Mile High City saw the mercury top out at 99 degrees. This easily bested the old record high for September 7th of 95 degrees set in 2013.

Additionally, the low temperature reading yesterday at the airport of 66 degrees set a record low minimum for the date. That easily bested the previous record of 63 degrees set in 1938 and previous years.

Thornton was again just a bit warmer during the day yesterday, recording a max of 100 degrees. This was Thornton’s seventh 100 degree reading of the year. Conversely, we were a good bit cooler than DIA with a low of 59 degrees.

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Thursday brings one more hot day to Thornton before a much-needed break arrives

Thursday, September 8th, 2022 5:33am MST

Hang in there, folks! You have to endure the heat one more day and the, mercifully, we will see much cooler temps for a few days. For today, sunny and smoky skies start us off like in recent days.

The afternoon will see clouds build up a bit and offer some breezy winds. High temperatures today are going to push close to the 100 degree mark. Denver’s record high for the date is 94 degrees (1959) and will almost certainly fall. Late afternoon and evening bring just a slight chance to see a thunderstorm.

Tonight, any storms will be done by about 11:00pm. Cloud cover will then ease. Overnight lows will dip to the upper 50s as the first cold front works its way through.

Looking ahead, that cold front coupled with another Friday night will bring about significant changes to our weather for Friday and the weekend. Get a preview in the extended weather forecast here.

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Wednesday in Thornton offers up more heat, areas of smoke

Wednesday, September 7th, 2022 5:01am MST

Today’s forecast is pretty much a carbon copy of yesterday’s. We will continue to see unusually warm temperatures and smoke from wildfires in neighboring states will color the skies.

Sunny / hazy skies will be the rule today throughout with a few clouds late. Overall conditions will be dry and calm. High temperatures will again be topping out in the mid to upper 90s.

Denver’s record high for the date is 95 degrees and that mark will possibly fall. A Heat Advisory will be in effect from 10:00am to 6:00pm. The extreme temperatures will increase the danger of heat-related illnesses so caution should be exercised.

Tonight, skies will be mostly clear with the smoke continuing. Overnight lows will be in the low to mid-60s.

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Record high minimum tied for September 6

Tuesday, September 6th, 2022 11:59pm MST

Record High Temperature

With the heat, one would hope for relief at night and in the early mornings. While it has cooled some overnight, it has remained unusually warm.

As measured at Denver International Airport, the low temperature today was 67 degrees. This ties the record high minimum for the date set in 2020.

Thornton was a good bit cooler with a low of 59 degrees.

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Denver sets record high temperature for September 6

Tuesday, September 6th, 2022 6:47pm MST

Record High Temperature

The heat is on and the records have begun to fall. Today Denver set a record high temperature and it likely is only the first of at least a few records that will fall in the coming days.

As measured at Denver International Airport, the Mile High City’s high temperature today topped out at 98 degrees. That just tops the previous record high for the date of 97 degrees set two years ago in 2020.

In Thornton, we were actually a slight bit warmer with a high of 99 degrees.

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