Thornton, Colorado, USA
UpdatedTue, 22-Sep-2020 3:20pm MDT 


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September snow in Denver is not entirely uncommon

Friday, September 4th, 2020 9:40am MDT
Denver September Snow History. (ThorntonWeather.com)

Denver September Snow History. Click for larger view. (ThorntonWeather.com)

There is lots of talk (and hype!) about next week’s storm and the potential for our first snowfall of the season. While it is somewhat unusual to get snow so early in the season, it is far from unprecedented and not near as rare as you might think.

Whipping out the weather history books, we see that snow has fallen in 28 Septembers in the 139 years since the National Weather Service began recording snow in the Mile High City. That equates to about 20% of the years.

It has, however, been quite a while since we have seen one, the most recent occurring in 2000. That was the last in a stretch in which six out of eight years saw September snow.

Our earliest snowfall on record came on September 3, 1961 when 4.2 inches of the white stuff fell. The average date of Denver’s first snow is October 18th.

Most concerning about these early season snows is the potential for tree damage and power outages. Like spring storms, early season snows are usually quite wet and heavy and have the potential to wreak havoc, even if there isn’t much to them.

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Thornton’s Labor Day weekend to feature lots of sun and lots of heat

Friday, September 4th, 2020 5:04am MDT

The only wrinkle Mother Nature will be throwing in your holiday camping and barbeque plans is the heat. Otherwise, the four day period looks to feature lots of sun and, overall, calm and dry conditions.

We start things off Friday with sunny skies and calm, dry conditions. Highs today will top out in the low 90s. Tonight, skies remain clear with overnight lows in the upper 50s.

Saturday brings on the heat. Sunny skies will be above and temperatures will climb to the upper 90s. Saturday night into Sunday morning, lows will drop to the low 60s under clear skies.

Sunday keeps the heat going but does bring some breezy winds. Sunny skies will be above with highs again in the mid to upper 90s. Look for winds to become a bit breezy in the afternoon as a weak cold front arrives. Sunday night into Monday morning, mostly clear skies will be above with lows in the upper 50s.

Labor Day will see things cool down a bit with highs in the upper 80s. The afternoon and evening bring a slight chance for a shower as a second front makes itself felt. Have a great weekend and be safe!

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Thornton cools a bit Thursday and will see near normal temps, sunny skies, calm conditions

Thursday, September 3rd, 2020 4:47am MDT

A cold front blew in early this morning and in the wake of its breezy winds, we will enjoy a pleasant day. Temperatures will cool to near-normal levels with nary a cloud in the sky.

The day starts off on the cool side and then we will gradually warm up. Highs today will be right near the average for the date of 83 degrees. Sunny skies will be above throughout with calm, dry conditions.

Tonight, skies remain clear and overnight lows will dip to the mid-50s.

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

Wednesday, September 2nd, 2020 5:09am MDT

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:


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.


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 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 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 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 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 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.

» Click here to read the rest of August 30 to September 5: This week in Denver weather history

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Thornton’s temperatures rebound Wednesday and return to above normal readings

Wednesday, September 2nd, 2020 4:59am MDT

Following a few days of cooler weather, the mercury is set to climb again today. We will be stringing together a number of mild days but, on the horizon, much cooler weather threatens next week.

For today, there is very little moisture to be had and that is going to allow for sunny skies throughout the day. Temperatures will be climbing to highs close to the 90 degree mark.

Tonight, skies remain clear with overnight lows in the low 50s.

Looking ahead, we will cool a bit tomorrow but then the 90s look to return through the weekend. We are currently closely watching a potent system that appears poised to bring much colder air down from the north next Tuesday.

If it pans out, this would lead to much colder temperatures and perhaps, dare we say, some snow for parts of the Front Range. At this time it looks like any of the white stuff would be confined to the foothills but it does bear close watching.

So, for now, enjoy that warmth!

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Thornton’s September weather preview: Usually a calm, pleasant month

Wednesday, September 2nd, 2020 3:01am MDT

Following an August 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.

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First day of September brings pleasant temperatures, calm conditions

Tuesday, September 1st, 2020 4:59am MDT

Following a light, overnight rain, #Thornton will enjoy a day with calm conditions and temperatures a bit below normal.

The day starts off with a few clouds, a sign of the moisture aloft, but those will dissipate as the day proceeds. Overall conditions will be calm and dry. Highs today will top out right near the 80 degree mark.

Tonight, skies will be clear with overnight lows in the low 50s.

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Thornton to enjoy a cooler start to the week, chance of showers

Monday, August 31st, 2020 5:08am MDT

This morning we saw our coolest temperature in over two and a half months. That cool start will be coupled with a similarly cool day, well, at least one much cooler than we have seen in recent weeks.

Sunny skies start us off them a few clouds will arrive but mostly clear skies will stick with us until about mid-afternoon. High temperatures today will top out right near the 80 degree mark, a few degrees below normal.

We begin to see a chance for a thunderstorm from late afternoon on with better chances for showers after 8:00pm until midnight. A few, light showers may linger after that.

Mostly cloudy skies will be above tonight with overnight lows in the low 50s.

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Thornton finally breaks out of the heat with cooler temps, chances for precipitation for the weekend

Friday, August 28th, 2020 5:06am MDT

Finally! It has been long overdue but we get out of the hot weather pattern of recent weeks starting today. Making it even better, we stand a decent chance to receive much-needed rain.

For Friday, mostly sunny skies will be the rule in the morning and then this afternoon cloud cover will increase. Highs today will be below normal and in the low to mid-80s. The afternoon brings some scattered thunderstorm activity with our best opportunity coming from 3:00pm to 8:00pm. Tonight, partly clear skies will be above and lows dip to the upper 50s.

Saturday continues the cooler temperatures with highs again in the low to mid-80s under partly sunny skies. Moisture will be increasing and that will give us a decent chance to see some PM showers. Saturday night into Sunday morning, any shower activity will end by midnight and partly cloudy skies will be above. Overnight lows will be in the upper 50s.

We close out the weekend on Sunday with a bit of a rebound in the temperatures. Mostly sunny skies will be above and highs will be in the upper 80s. There will be just a slight chance for a PM thunderstorm but activity at this time looks to be quite isolated. Enjoy the break from the heat

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Thornton gets one more hot day before relief from the heat arrives

Thursday, August 27th, 2020 4:59am MDT

Following yesterday’s much-needed shower, today sees the heat return and less of a chance for storms. However, a cold front will be moving through tonight serving to cool things down for Friday and the weekend.

Sunny but hazy skies start us off today then we will see a few clouds in the late morning and afternoon as usual. Highs today will once again be well above normal, topping out around 97 degrees. Mid to late afternoon through the evening bring just a slight chance for storms but, at this time, those are looking to be pretty widely scattered.

Tonight, any storm activity will end by midnight and skies will be mostly clear. Overnight lows will be in the low 60s.

Looking ahead, a cold front moves through late tonight and with it cooler temperatures and better chances for precipitation will be seen Friday and for the weekend. Then, a second front on Monday should cool us down even further. Get a sneak peek at your weekend forecast here.

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