Thornton, Colorado, USA
UpdatedTue, 03-Oct-2023 12:10pm MDT 


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Thornton’s September 2023 preview: Usually one of the most pleasant months of the year

Monday, September 4th, 2023 3:02am MDT

Following an August that was unseasonably warm, 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.

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September 3 to September 9: This week in Denver weather history

Sunday, September 3rd, 2023 5:33am MDT

This Week in Denver Weather History

The first full week of September sees us start one of the most pleasant times of year in Denver. While less common this time year, severe weather can and does occur. Our look back at this week in Denver weather history includes hail, damaging wind and even smoke from wildfires hundreds of miles away.

From the National Weather Service


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.


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.


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 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.


In 1901…a thunderstorm produced rain…hail of unknown size… And south winds sustained to 40 mph with gusts to 43 mph.

In 1961…Labor Day snow storm is the earliest date of the first snow…trace and measurable…of the season. The heavy wet snow broke many limbs from trees that were still in full foliage. The storm produced 4.2 inches of snowfall at Stapleton Airport with nearly a foot of snow in western suburbs and in the foothills. Minimum temperature of 33 degrees was a record for the date and the coldest ever recorded so early in the season.

In 1999…severe thunderstorms dumped large hail across metro Denver. Hail as large as 1 inch in diameter was measured near Cherry Creek in Aurora and near Bennett. Hail to 3/4 inch in diameter fell in the city of Denver.

In 2002…a thunderstorm produced a wind gust to 51 mph at Denver International Airport.

In 2003…very heavy thunderstorm rain washed out parts of the Virginia Canyon Road above Idaho Springs. Up to 4 feet of mud reportedly washed down the road during the storm. Several vehicles were trapped on the road.

In Idaho Springs…several streets…including the main street… Were also buried in mud and gravel. Some buildings in town experienced minor flooding…including the basement of the town library and the police station.


In 1909…rainfall for the 4 days accumulated to 3.97 inches in Boulder…while in Denver rainfall totaled 2.45 inches on the 4th…5th…and 6th.


In 1909…apparent post-frontal heavy rainfall totaled 1.94 inches in downtown Denver. North winds were sustained to 19 mph.

In 1944…a trace of rain fell. This together with a trace of rain on the 9th…10th…and 30th was the only precipitation for the month. The total of a trace of precipitation for the month equaled the driest September on record first set in 1892.

In 1960…the highest recorded temperature in September…97 degrees…occurred. The same temperature also occurred on September 5…1899…September 1…1995…and September 4… 1995.

In 1989…a strong thunderstorm wind gust flipped a plane taxiing on a private runway in Adams County east of Denver. Two people were slightly injured and the plane was heavily damaged.

In 1992…strong winds developed across metro Denver behind a pacific cold front. Sustained winds above 40 mph with gusts as high as 60 mph were recorded mainly in and near the foothills. Pre-frontal south winds gusted to 37 mph at Stapleton International Airport.

In 1995…two people were injured when lightning struck their home in Lakewood. The lightning entered the attic where it started a small fire. It then traveled through the walls… Exploding a mirror and spraying glass on the residents. Lightning also sparked small grass fires near Aurora…Denver International Airport…and Bennett. The highest recorded temperature in September…97 degrees…occurred. The same temperature also occurred on September 5…1899…September 4…1960…and September 1…1995.

In 2000…thunderstorm winds gusted to 64 mph in Castle Rock.


In 1899…the highest recorded temperature in September…97 degrees…occurred. The same temperature was also reached on September 4…1960…and September 1 and 4…1995.

In 1940…a severe wind and hail storm confined mostly to the west and north parts of the city occurred shortly after 4:30 pm. Hail stones ranged in size from 1/4 to 1/2 inch in diameter. In north Denver…hail piled to a depth of 4 inches. Flooding occurred in one underpass…which stalled 2 cars. One girl was injured when the weight of the hail flattened a porch on which she stood. Northeast winds were sustained to 29 mph with gusts to 32 mph in downtown Denver.

In 1987…a thunderstorm complex produced hail as large as 1 3/8 inches in diameter…2 miles east of Buckley Field in Aurora. No damage was reported.


In 2020…a strong upper level low brought an end to record heat to the Front Range urban corridor…and provided Denver its second earliest measurable snowfall on record. Numerous heat records were set leading up to the snowfall…and several new snowfall and cold records were also broken in this abrupt bout with winter. Denver set its all time record high for September…reaching 101 degrees during the afternoon. This was also the latest date a 100 degree reading has ever been observed in Denver. Another daily record high was then tied on September 6th when Denver hit 97 degrees. September 7th was the last day of heat when Denver`s high temperature reached 93 degrees. That tied Denver for the record for the number of 90 degree days for a year at 73…and was also the warmest temperature ever recorded before a day of measurable snowfall. By the evening of September 7th…a series of cold fronts progressed southward from Wyoming into Colorado… dropping the temperature into the low 30s by the early morning hours of September 8th. Snow developed across the Front Range mountains and foothills overnight… while a mix of rain and snow developed along the I-25 corridor. A few locations picked up light snowfall accumulations in the morning. Accumulating snow was mostly confined to the higher elevations much of the day…before spreading across the plains during the late afternoon and evening. Storm totals ranged from 4 to 10 inches in the mountains…with 3 to 6 inches near the foothills. A total of 5.6 inches of snow was measured at the NWS Boulder office…while at Denver International Airport…the official measurement was 1.0 inch. » Click here to read the rest of September 3 to September 9: This week in Denver weather history

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Denver ties record high minimum for September 2

Saturday, September 2nd, 2023 11:59pm MDT

Record High Temperature

Following on yesterday’s record high temperature, today’s low end did not get particularly cool and, in fact, tied a record.

As measured at Denver International Airport, the Mile High City’s low temperature for September 2 came in at 67 degrees. This tied the record for warmest low temperature for the date last set in 1939.

Here in Thornton, we cooled down to far more normal levels. Our low for the date was 61.7 degrees.

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Denver sets record high temperature for September 1

Friday, September 1st, 2023 7:46pm MDT

Record High Temperature

While it may be the first day of meteorological autumn, Mother Nature isn’t giving up on summer yet.

As measured at Denver International Airport, the Mile High City hit a high temperature today of 99 degrees. This breaks the previous record high for the date of 98 degrees set in 2019.

Here in Thornton, we bested Denver by one degree with a high of 100 degrees.

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Labor Day weekend in Thornton to feature above normal temps, few chances for precipitation

Friday, September 1st, 2023 4:51am MDT

The hot temps of recent days are going to continue right on into the first half of the four-day period. We will then see some cooling but not much.

Friday looks much like the last couple with perhaps a few more clouds. Look for highs in the mid to upper 90s under mostly sunny skies. Tonight, lows will dip to the mid-60s under partly cloudy skies.

Saturday starts out sunny then in the afternoon a few clouds arrive as well as some breezy winds. Highs will be in the mid-90s. Saturday night, it will be partly cloudy with lows in the mid-60s.

Sunday will be sunny initially and highs will be in the low to mid-90s. The afternoon and evening bring just a slight chance for a thunderstorm. Sunday night, skies will become mostly clear and lows will be around 60 degrees.

For Labor Day, temps cool a bit further with highs in the upper 80s expected. The afternoon again brings just a slight chance for a thunderstorm.

Have a fantastic weekend!

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Another hot one Thursday for Thornton with temps well above normal

Thursday, August 31st, 2023 4:53am MDT

Mother Nature isn’t quite ready to give up on the summer heat yet. Today looks much like yesterday with hot temps, dry conditions.

Sunny skies start us off and will be with us most of the day. The late afternoon and evening may bring a few clouds and some breezy winds. Highs will again top out in the mid to upper 90s.

Tonight, skies will be mostly clear with overnight lows in the low 60s.

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The heat stages a return for Thornton’s Wednesday

Wednesday, August 30th, 2023 4:55am MDT

After stringing together five cooler days, the heat returns for the next few. Temps today will be well above normal but it will be calm and dry.

Sunny skies will be with us for most of the day. The mid to late afternoon may see a few clouds. High temperatures are going to top out in the mid-90s, well above the average high for the date of 85 degrees.

Tonight, skies will be mostly clear with lows around the 60 degree mark.

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Tuesday offers up pleasant weather with temps near normal, calm conditions

Tuesday, August 29th, 2023 4:49am MDT

A fine looking day on tap for Thornton. Look for lots of sun above, calm conditions and temps right near average.

Sunny skies will be above throughout the day today as moisture has decreased significantly. Overall, conditions will be calm and dry. Highs will top out right near the average high for the date of 85 degrees.

Tonight, skies will remain clear with lows dipping to the mid-50s.


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August 2023 top shots: Monthly photo slideshow

Monday, August 28th, 2023 6:57pm MDT
A beautiful rainbow as a thunderstorm passes. (Bill Hutchinson)

A beautiful rainbow as a thunderstorm passes. (Bill Hutchinson)

As the calendar turns to August, the summertime heat begins to fade and that makes it easier to get out and enjoy all of the outdoor activities Colorado has to offer.  From a walk in a park to afternoon thunderstorms to an abundance of wildlife, photo opportunities abound as is seen in our slideshow.

Our monsoon season typically arrives about now and that means better chances for moisture.  However with limited instability, the intensity of storms are more sedate.  That doesn’t mean however that the weather is any less photographic.

  • Slideshow updated August 29, 2023

By the end of the month some of our seasonal feathered friends will be looking to leave the state giving our last chance to see them till spring.  Larger mammals are gearing up for the rut (mating season) and that can make for some intense scenes.

Showcasing images captured by ThorntonWeather.com readers as well as some of our own, our monthly slideshow covers the entire gamut of weather and nature related imagery. Sunsets, sunrises, wildlife and of course every type of weather condition are vividly depicted.

To learn more about how to send your photo to us for inclusion in the slideshow, see below the slideshow.

What is missing in the slideshow above?  Your photo!

Our monthly photo slideshow is going to feature images that we have taken but more importantly images that you have captured.  The photos can be of anything even remotely weather-related.

Landscapes, current conditions, wildlife, pets, kids.  Whimsical, newsy, artsy.  Taken at the zoo, some other area attraction, a local park, a national park or your backyard.  You name it, we want to see and share it!

Images can be taken in Thornton, Denver or anywhere across the extraordinary Centennial State.  We’ll even take some from out of state if we can tie it to Colorado somehow.

We’ll keep the criteria very open to interpretation with just about any image eligible to be shown in our slideshows.

What do you win for having your image in our slideshow?  We are just a ‘mom and pop’ outfit and make no money from our site so we really don’t have the means to provide prizes.  However you will have our undying gratitude and the satisfaction that your images are shared on the most popular website in Thornton.

To share you images with us and get them included in the slideshow just email them to us or share them with ThorntonWeather.com on any of the various social media outlets.  Links are provided below.

So come on, get those camera’s rolling!

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Cooler temperatures, a good chance for storms start off Thornton’s workweek

Monday, August 28th, 2023 5:12am MDT

The weekend ended up being milder and drier than originally expected. Today, we see things cool down and should receive some showers and thunderstorms.

Partly cloudy skies start things off and cloud cover will be increasing in the morning as moisture streams in. Temperatures will top out right around the 80-degree mark. Mid-morning we begin to see just a slight chance for a shower with opportunities increasing after 1:00pm, becoming likely from 3:00pm to 6:00pm.

This evening, a few storms / showers may linger until midnight. Then skies will begin to clear and overnight lows will dip to the mid to upper 50s. Keep an eye out for those storms with our interactive radar here.

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