Thornton, Colorado, USA
UpdatedMon, 20-Feb-2017 3:50am MST 


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Thornton breaks out of the chill for Friday and the weekend

Friday, December 9th, 2016 5:25am MST

Following a few days of Arctic cold, we see a return to more seasonal type temperatures and conditions for the three-day period. Overall warmer mercury readings and calmer weather conditions can be expected but a weak disturbance may mix things up just a bit Saturday. All-in-all, it should be a decent weekend for the city’s annual Winterfest.

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For Friday we start out quite cold and in the single digits. However we will be warming up nicely with highs right around 40 degrees – as long as the lingering snow cover doesn’t inhibit temperatures too much. Look for mostly sunny skies above throughout the day. Tonight we’ll be dipping down with lows in the low 20s.

On Saturday we will see mostly to partly sunny skies for most of the day with some increase in cloud cover in the afternoon and evening as a disturbance pushes through. Look for high temperatures in the upper 40s. As that system moves in, we stand just a slight chance to see a sprinkle of rain in the afternoon then a few snowflakes overnight and into Sunday morning. Lows Saturday night will be down to the mid to upper 20s.

Sunday starts out with the potential for a few lingering flurries and mostly cloudy skies. However as we get later into the morning cloud cover will decrease leaving partly to mostly sunny skies for the rest of the day. Temperatures will be topping out right near the average of 43 degrees.

Looking into next week, Monday should be somewhat similar to this weekend with dry conditions and temperatures close to normal. After that, we are watching another blast of cold air set to impact us starting Tuesday. Right now it doesn’t look like the cold with it will be extreme as the last blast but it will have a definite impact toward the colder side of things.

Have a great weekend!

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John Glenn, First US Astronaut to Orbit the Earth, Dies at 95

Friday, December 9th, 2016 4:17am MST

John Glenn, the first U.S. astronaut to orbit the earth, has died at age 95, officials said. Glenn passed away Thursday, more than a week after being admitted to the Ohio State University’s James Cancer Hospital. The John Glenn College of Public Affairs at OSU made the announcement. U.S. President Barack Obama issued a statement saying… » Click here to read the rest of John Glenn, First US Astronaut to Orbit the Earth, Dies at 95

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The sun and dry conditions return but the Arctic cold remains

Thursday, December 8th, 2016 5:13am MST

Our latest storm system has moved out and as long as you are looking out a window from the inside, today won’t seem too bad. Step outside though and you will be hit with the realization that we are seeing some extremely cold temperatures.

We start out the day with mercury readings well below zero, the first time we have gone negative since January 5, 2015. This type of cold is certainly not unusual but it doesn’t make it any more tolerable. Early on there will be some fog in low-lying areas, particularly along the Platte, so be careful. After that we’ll see mostly sunny skies throughout.

Despite the sun, temperatures are going to struggle to recover and we expect to see a high only in the mid to upper teens. Bundle up if you head out! How cold is it right now? Check our live gauges.

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Wednesday to see snow ending, cold to remain in place

Wednesday, December 7th, 2016 5:35am MST

Unfortunately we didn’t end up with the snow accumulations we had hoped for as drier air kept things from materializing quite as expected. While the snow will be coming to an end, the cold will linger and make things uncomfortable outside.

We start out under cloudy skies and light snow. Look for the white stuff to taper off with only a few flurries by mid-morning then ending entirely by noon. Only light additional accumulations are expected. By the end of the day we should start to see the sun make an appearance.

In terms of temperatures, readings are going to stay relatively constant today and quite cold. Look for a high in the teens.

Tonight, with clearing skies, the mercury is going to plunge to below zero. Assuming it does, this will be our first time in sub-zero territory in 23 months.

Please allow extra time this morning for your commute and stay warm.

Keep an eye on the temperature here.

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November 2016 weather recap: Month was much warmer than normal, offered little precip

Tuesday, December 6th, 2016 2:18pm MST

The month of November 2016 was certainly an unusual one for Thornton.  Despite a turn toward colder weather at the end, the extraordinary warmth at the start was the dominating feature. We did finally receive our first snow of the season although we are far behind normal for the season.

Dominating high pressure was a recurring theme for the first half of the month.  This kept storm systems and colder temperatures at bay bringing unseasonably warm mercury readings.  Every one of the first 16 days of the month saw temperatures in excess of 60 degrees, five saw readings warmer than 70 degrees and one even hit over 80 degrees.

A series of troughs and cold fronts finally brought an end to the record-setting warmth.  After recording 81.5 degrees of the 16th, we followed with a 40.9 degree high on the 17th.  The 17th also brought our first, and thus far only, snowfall of the season.  The balance of the month saw things return to a more typical November weather pattern.

Thornton’s average monthly temperature for November 2016 came in at 43.9 degrees.  This was far above Denver’s historical average for the month of 38.3 degrees.  Out at the airport where the Mile High City’s official measurements are kept, the average came in warmer still at 45.1 degrees.  That put November 2016 into the books at the 10th warmest November in Denver weather history.

Temperatures in Thornton ranged from the aforementioned high of 81.5 degrees on the 16th down to a low of 13 degrees on the morning of the 30th.  DIA’s high was 80 degrees and its low 10 degrees, each on the same day as Thornton’s maximum and minimum.  The 80 degree reading on the 16th was not only a record for the date but also the latest 80 degree temperature ever recorded in Denver.

In terms of precipitation, Denver averages 0.61 inches during the month of November.  Thornton fell far short of that with a mere 0.24 inches of precip in the bucket. Out at the airport, Denver fared better with 0.52 inches.

Thornton recorded 2.2 inches of snow for the month while Denver ended with 1.7 inches.  Both were far below the November average of 8.7 inches and comprise the only snowfall we have seen this season.  The snow on the 17th was the third latest first seasonal snowfall on record in Denver.

Click here to view Thornton’s November 2016 climate report.

Thornton, Colorado's November 2016 temperature summary. (ThorntonWeather.com)

Thornton, Colorado’s November 2016 temperature summary. (ThorntonWeather.com)

Thornton, Colorado's November 2016 precipitation summary. (ThorntonWeather.com)

Thornton, Colorado’s November 2016 precipitation summary. (ThorntonWeather.com)

From the National Weather Service:

638 AM MST THU DEC 1 2016




                 VALUE   DATE(S)  VALUE   FROM    VALUE  DATE(S)
 HIGH              80   11/16/2016
 LOW              -18   11/29/1877
HIGHEST            80R  11/16        73       7       75  11/03
LOWEST             10   11/30         6       4        3  11/27
AVG. MAXIMUM     59.9              52.1     7.8     51.2
AVG. MINIMUM     30.4              24.5     5.9     25.7
MEAN             45.1              38.3     6.8     38.5
DAYS MAX >= 90      0               0.0     0.0        0
DAYS MAX <= 32      1               2.3    -1.3        5
DAYS MIN <= 32     15              23.4    -8.4       24
DAYS MIN <= 0 0 0.6 -0.6 0 PRECIPITATION (INCHES) RECORD MAXIMUM 3.21 1946 MINIMUM T 1899 1901 1949 TOTALS 0.52 0.61 -0.09 2.13 DAILY AVG. 0.02 0.02 0.00 0.07 DAYS >= .01         2               4.7    -2.7       11
DAYS >= .10         2               1.6     0.4        6
DAYS >= .50         0               0.0     0.0        1
DAYS >= 1.00        0               0.0     0.0        0
 24 HR. TOTAL    0.30   11/22 TO 11/22           11/04 TO 11/05

 TOTAL            1.7               8.7
RECORD NOVEMBER  42.5                      1946

HEATING TOTAL     586               801    -215      789
 SINCE 7/1        896              1382    -486     1090
COOLING TOTAL       0                 0       0        0
 SINCE 1/1        878               769     109      877

 EARLIEST     09/08/1962
 LATEST       06/08/2007
EARLIEST                        10/07
LATEST                          05/05

AVERAGE WIND SPEED              9.8

AVERAGE SKY COVER           0.40
NUMBER OF DAYS FAIR           14
NUMBER OF DAYS PC             12


THUNDERSTORM              0     MIXED PRECIP               0
HEAVY RAIN                0     RAIN                       1
LIGHT RAIN                1     FREEZING RAIN              0
LT FREEZING RAIN          0     HAIL                       0
HEAVY SNOW                1     SNOW                       1
LIGHT SNOW                2     SLEET                      0
FOG                       2     FOG W/VIS <= 1/4 MILE      1
HAZE                      1

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Thornton’s December preview: With arrival of winter, cold and snow increase

Tuesday, December 6th, 2016 11:32am MST

The month of December brings with it the official start of winter and oftentimes, colder and snowier weather conditions. It however can also offer unseasonably warm temperatures and bone dry conditions.  Given our recent mild and dry weather, we are certainly hoping for a change in the coming month.

Overall December’s monthly mean temperature of 30.0 degrees (1981 – 2010 averages) makes it our coldest month.  Snow is always on everyone’s mind this time of year but December is only our 3rd snowiest month behind March and November with an average of 8.5 inches of the white stuff.

We closed out November quite wet and chilly and that is expected to continue into the first part of December.  Long term models then point to a continuation of above normal precipitation but near normal temperatures.

Get all the details on Thornton’s December weather including a look back at historical events and a look at the long range forecast in our December weather preview here.

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Wintry blast set to impact Thornton with bitter cold and snow

Tuesday, December 6th, 2016 5:17am MST

The much-anticipated (perhaps dreaded) storm is working its way toward us and while delayed a bit, is still expected to have the impact on our weather we have been talking about. We will see a significant change in temperatures as well as our second snowfall of the season.

We start out the day with some sun but clouds will gradually be increasing as the day progresses. Temperatures today will top out close to the freezing mark, likely a couple of degrees below.

The afternoon may bring some flurries but right now it looks like snow won’t start spreading until after 6:00pm. From there it is expected to last into tomorrow morning. The later arrival may spare this evening’s commute much heartache but tomorrow morning’s could be a rough one. Overnight tonight temperatures will dip into the single digits.

A Winter Weather Advisory is in effect from 6:00pm this evening until noon Wednesday. That means that travel could become difficult with slick roads and limited visibilities. Please be careful.

For all the latest, head over to our Winter Weather Briefing Page.

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Thornton to start out the workweek warm but big changes arrive soon

Monday, December 5th, 2016 5:17am MST

We will enjoy one more mild day Monday, albeit with some wind, then the weather will change considerably. The mid-week is going to feature bone-chilling cold and even a shot of snow.

For today look for mostly to partly sunny skies to be above throughout. Warming, downslope winds will be breezy at times, particularly from late morning into the evening.

Temperatures today will climb to highs in the low 50s. Overnight tonight we will begin to feel the effects of the approaching system as temperatures drop to the teens.

We will then see three days straight with mercury readings failing to climb above freezing and in fact will be well below Wednesday and Thursday.

In terms of snow, we may see a flurry overnight tonight but with little or no accumulation. The best chances will come tomorrow afternoon into Wednesday morning. How much? It is still a bit early and models are not in agreement but we do see the potential for 3 to 6 inches for the entire event.

We’ll get a better feel for it over the next 24 hours. In the meantime, enjoy today’s relative warmth and use our Winter Weather Briefing Page as your one-stop-shop for the coming storm.

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December 4 to December 10: This week in Denver weather history

Sunday, December 4th, 2016 4:34pm MST
This Week In Denver Weather History

December 4 to December 10: This week in Denver weather history

As we have seen in recent days, Old Man Winter oftentimes makes his appearance in earnest during the month of Denver. Looking back at this week in Denver weather history we can see that is not at all unusual.

From the National Weather Service:


In 1913…the 1st marked the start of the heaviest 5-day total snowfall in the city’s history. During this period snowfall totaled 45.7 inches. Starting on the 1st…snow fell intermittently for 3 days and accumulated a little over 8 inches. On the 4th and 5th…an additional 37.4 inches of snow fell. At Georgetown in the foothills west of Denver even more snow fell…86 inches over the 5 days with the most…63 inches…on the 4th. In Colorado…snowfall was heavy along the eastern slopes of the mountains from the Palmer Divide north. High winds during the storm caused heavy drifting…which blocked all transportation. Snow cover of an inch or more from the storm persisted for 60 consecutive days from the 1st through January 29…1914. Additional snowfall in December and January prolonged the number of days. This is the third longest period of snow cover on record in the city.


In 1909…post-frontal snowfall totaled 6.1 inches in downtown Denver. Most of the snow…5.9 inches…fell between 6:00 pm on the 2nd and 6:00 pm on the 3rd. North winds were sustained to 18 mph on both the 2nd and 3rd.


In 1939…more than 2 weeks of unseasonably warm weather made the month the 3rd warmest on record. Seven daily temperature records were set…including the all time record high temperature for the month of 79 degrees on the 5th. Daytime highs were balmy with 14 days in the 60’s and 70’s. Low temperatures dipped to freezing or below on only 5 days. The period was dry with only a trace of snow on the 12th.


In 1968…strong Chinook winds in Boulder gusting to 52 mph downtown caused 7 thousand dollars in damage. Flying debris damaged cars…houses…and other property in Boulder. West winds gusted to 49 mph late on the 3rd and to 45 mph on the 4th at Stapleton International Airport where the temperature climbed to a high of 60 degrees on the 4th.

In 1970…strong winds whistled through Boulder. Sustained winds of 40 mph with gusts to 70 mph were recorded at the National Bureau of Standards in Boulder. Wind gusts to 50 mph occurred in downtown Denver. No damage was reported. On the 3rd…northwest winds gusted to 40 mph at Stapleton International Airport where the Chinook winds warmed the temperature to a high of 66 degrees on the 4th.

In 1999…heavy snow fell over the foothills and metro Denver. The heaviest snowfall occurred in the foothills south of I-70 and near the Palmer Divide. Snowfall totals included: 25 inches near Tiny Town; 18 inches at Conifer; 15 inches near Evergreen; 14 inches at Chief Hosa…8 miles west of Castle Rock…and near Blackhawk; 12 inches at Pine Junction and 8 miles south of Sedalia; 11 inches atop Floyd Hill and in Roxborough; and 10 inches at Castle Rock. Around metro Denver…snowfall totals included: 10 inches at Highlands Ranch…9 inches at Parker…and 8 inches in Aurora and Wheat Ridge. Elsewhere around the metro area…snowfall generally ranged from 3 to 5 inches. Only 3.2 inches of snow fell at the site of the former Stapleton International Airport. North winds gusted to 32 mph at Denver International Airport on the 3rd.

In 2007…high winds developed in and near the Front Range foothills. Peak wind reports included: 88 mph atop Niwot Ridge; 87 mph atop mines peak; 80 mph…3 miles southeast of Jamestown; 78 mph at Longmont; 74 mph at Table Mesa. A few power outages occurred in Longmont as broken branches downed power lines. Northwest winds gusted to 38 mph at Denver International Airport on the 4th.

In 2013…a storm system brought heavy snow to parts of the Front Range Foothills. Storm totals included: 12 inches…7 miles west-southwest of Evergreen; 10.5 inches…3 miles north of Bailey; 9.5 inches…3 miles west of Jamestown and 5 miles northeast of Ward; 9 inches in Bailey…8.5 inches… 3 miles north of Conifer.


In 1972…a protracted cold spell held an icy grip on metro Denver when maximum temperatures never reached above freezing for 10 consecutive days from the 3rd through the 12th and minimum temperatures dipped below zero on eleven consecutive days from the 5th through the 15th. Daily low temperature records were set with 15 degrees below zero on the 5th…17 degrees below zero on the 6th… And 18 degrees below zero on the 10th. Daily record low maximum readings were set with 3 degrees on the 6th and 6 degrees on the 9th. The very cold temperatures were caused by 3 to 5 inches of snow cover and a Canadian air mass.


In 1884…a windstorm during the afternoon produced sustained northwest winds to 34 mph with higher gusts. The strong wind blew one of the wooden slats from the weather instrument shelter…which broke the wet-bulb thermometer.

In 1885…north winds were sustained to 40 mph during the early morning hours. The strong winds were accompanied by a cold wave.

In 1893…northwest winds were sustained to 48 mph with gusts as high as 55 mph. The Chinook winds warmed the temperature to a high of 58 degrees.

In 1901…Chinook winds sustained from the northwest at 40 mph with gusts to 48 mph warmed the temperature to a high of 55 degrees in the city.

In 1906…rainfall of only 0.01 inch before daybreak was the only measurable precipitation of the month…ranking the month the third driest December on record.

In 1910…cold west winds were strong all day with a sustained speed to 44 mph.

In 1977…northwest winds gusted to 55 mph at Stapleton International Airport where the strong Chinook winds warmed the temperature to a high of 55 degrees.

In 1978…high winds from 50 to near 150 mph occurred in the Boulder area. A pick-up truck was overturned…and a camper top was blown off another truck. Some roof damage was reported. Northwest winds gusted to 48 mph at Stapleton International Airport…where the Chinook winds warmed the temperature to a high of 57 degrees.

In 1980…wind gusts of 50 to 60 mph occurred along the foothills. Southwest winds gusted to 31 mph at Stapleton International Airport. The Chinook winds warmed the temperature to a record high of 69 degrees for the day.

In 1991…a volcanic ash cloud high in the atmosphere was clearly visible during the late afternoon being illuminated by the setting sun.

In 1995…very strong downslope winds gusting to 100 mph in the foothills knocked down trees and power lines… Triggering 800 power outages. Downed power lines sparked a half dozen brush fires ranging up to 4 acres in size. In Boulder…a portion of an old drive-in movie screen was blown down…and several car windows were shattered. The strongest wind gusts recorded were 100 mph at Golden Gate Canyon…99 mph at Rocky Flats Environmental Technology site…96 mph in north Boulder…94 mph at Wondervu…81 mph at Conifer…and 77 mph in south Boulder. West-northwest winds gusted to only 29 mph at Denver International Airport.


In 1912…5.2 inches of post-frontal snow fell in downtown Denver. Most of the snow fell on the 4th when northeast winds were sustained to 42 mph with gusts to 46 mph.

In 1913…a major winter storm produced heavy snowfall and blizzard conditions in the city. The snow fell continuously for 40 consecutive hours from 4:30 am on the 4th until just before midnight on the 5th and totaled 37.6 inches. The greatest accumulation on the ground was 32.6 inches at 6:00 pm on the 5th. Strong north winds accompanied the storm with sustained speeds of 30 mph or more for more than 25 hours. The highest sustained wind velocity was 44 mph during the afternoon of the 5th. Winds gusted to 46 mph on the 4th and to 47 mph on the 5th. The winds piled the snow into 4-and 5-foot drifts. By noon on the 4th traffic was interrupted…and by evening the heavy wet snow had blocked most streets and highways. Street cars stalled when streets became blocked. Automobiles and other conveyances were abandoned in the streets. By the 5th… The blockage extended to steam railroads. Flat roofed buildings collapsed…including the roof of the Calvary Baptist Church. Many downtown workers were unable to make it home on the night of the 4th and filled downtown hotels to overflowing. Some enjoyed the festive mood of the occasion and partied through the night. The city auditorium…jail…and several movie houses served as shelters for hundreds of people. The snow was remarkably moist for this time of year with a total water content of 3.44 inches. Temperatures during the storm were between 25 and 34 degrees. Cold weather followed the storm and snow remained on the ground for a long time. On some street car lines…it took 6 to 7 days before the right of way could be cleared. The foothills measured even more snow from the storm. At Georgetown…the 2 day snowfall totaled 71 inches. The 2.12 inches of precipitation measured on the 4th is the greatest calendar day precipitation ever recorded during the month of December in Denver. The 2.29 inches of precipitation measured from the 4th into the 5th is the greatest 24 hour precipitation ever recorded in the city during December.

In 1972…only 4.5 inches of snow fell at Stapleton International Airport…but high winds on the evening of the 4th caused blizzard conditions over the plains east of Denver. A 21-year-old University of Colorado student caught in the storm while cross country skiing west of Boulder froze to death. North winds gusted to 32 mph at Stapleton International Airport.

In 1979…the Front Range was hit by strong Chinook winds. The Boulder area was hardest hit with winds gusting to 119 mph at Rocky Flats and 92 mph in the city. A wind gust to 104 mph was recorded at Wondervu. Damage was widespread…amounting to 1.2 million dollars mainly around Boulder. Roofs were blown off several buildings and homes… Hundreds of windows were broken…and many cars were damaged by flying debris. Small planes were severely damaged at 3 airports in the area. West winds gusted to 55 mph at Stapleton International Airport on the 5th.

In 1996…persistent westerly flow aloft produced more high winds in and near the Front Range foothills. Several locations reported hurricane force winds with peak gusts of 100 to 120 mph. The high winds downed trees and power lines…leaving 700 residents without power for nearly 4 hours in the communities of beaver brook…blue valley… Conifer…Evergreen…and Floyd Hill. A wall of a building under construction in Lafayette was toppled…a semi-truck was blown over near the Boulder turnpike damaging a concrete barrier…and a 60-foot tree crushed a parked pick-up truck at a Denver residence. High wind gusts included: an estimated 120 mph at Blackhawk…115 mph at Aspen Springs…100 mph at the Eldora Ski Resort…75 mph atop Shanahan Ridge near Boulder…74 mph near Conifer…and 71 mph at the Rocky Flats Environmental Test Facility. At Denver International Airport…west winds gusted to 51 mph on the 4th and to only 38 mph on the 5th.

» Click here to read the rest of December 4 to December 10: This week in Denver weather history

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Thornton’s weekend starts cold with chance for snow then will warm up

Friday, December 2nd, 2016 5:02am MST

The three day period offers a little bit of a mixed bag of weather. A disturbance moving through today will keep things chilly and may drop just a little bit of snow. After that however, we see improving conditions and warming temperatures Saturday and Sunday.

For Friday look for mostly cloudy skies to be above. Some light snow / flurries will be possible with the best opportunity coming this afternoon. Temperatures will be cold with highs topping out in the mid-30s today. Overnight tonight skies will be begin to clear and temperatures drop to the teens.

Saturday will still have a few clouds but offer up mostly sunny skies overall. Conditions will be calm and dry as we head to a high in the mid-40s.

We close out the weekend with the most pleasant day of the period. Look for a healthy dose of sun Sunday with temperatures climbing to highs right near the 50 degree mark.

All eyes remain on the Arctic air mass that is working its way down to us and will bring big changes starting Tuesday. We’ll see temperatures plunge for a few days but are not currently expecting much in the way of snow. More in our extended forecast.

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