Category Archives: Climatology

Climatology, Thornton Weather

Astronomical winter arrives Saturday, offers up the shortest day of the year

The Winter Solstice
Winter officially begins at 2:21am MST on Saturday, December 21, 2024.

Astronomical winter arrives in Thornton early Saturday morning and with the solstice also comes the shortest day of the year.

Winter officially begins at 2:21am MST on Saturday, December 21, 2024.

The Winter Solstice occurs when the North Pole is tilted at its furthest from the sun – 23.5 degrees away. This results in the shortest day of the year in the Northern Hemisphere.

Here in Denver, with sunrise at 7:17am and sunset at 4:39pm, our day Saturday will be 9 hours, 21 minutes and 15 seconds long.

The following day, Sunday, it will be about three seconds longer and each day from now through to the Summer Solstice in June will get gradually longer as well.

While we have a short day on the solstice, it is nothing like what will be experienced in the Arctic Circle.  Areas north of there to the North Pole will have no direct sunlight at all.  Conversely, areas south of the Antarctic Circle toward the South Pole will have 24 hours of daylight and have a midnight sun.

Did you know that there is a difference between the astronomical seasons that we are discussing here and meteorological seasons?

Meteorological seasons differ slightly and are geared toward matching the calendar with the annual temperature cycle. This is done primarily for meteorological observing and forecasting and in many ways it is more logical than the astronomical seasons.

For the Northern Hemisphere, the meteorological spring covers the months of March, April and May. Summer brings the hottest months of the year and so meteorological summer is June, July and August. Meteorological fall then is September, October and November followed by the coldest months of December, January and February as meteorological winter.

Climatology, Thornton Weather

Denver’s Christmas weather history shows it isn’t usually a white one

Historical probability of at least 1 inch of snow on the ground on Christmas. (NOAA)
Historical probability of at least 1 inch of snow on the ground on Christmas. (NOAA)

As Christmas gets closer everyone always wonders if we are going to get the proverbial white Christmas. Unfortunately, if you look at Denver and Thornton weather history, the chances aren’t all that good but it also depends on what you define as a white Christmas.

If to you a white Christmas means having actual snowfall on Christmas Day the chances are pretty poor. But, if simply having snow on the ground suffices, the chances improve considerably.

For a complete look at Denver’s Christmas weather statistics, click here.

For the latest Thornton weather forecast for Christmas, check out our forecast page.

Climatology, Thornton Weather

November 2024 weather recap: We finally chill out, get a healthy dose of precipitation

Thornton, Colorado's November 2024 Temperature Summary. (ThorntonWeather.com)
Thornton, Colorado’s November 2024 Temperature Summary. (ThorntonWeather.com)

After eight months straight of above average temperatures and six months straight of below average precipitation, we finally broke the streaks in November. Temperatures cooled a good bit and we received well above normal levels of precipitation.

The first five days of the month continued the mild weather but we did receive some rain during that time which was welcome.  After that, we saw a somewhat prolonged period of unsettled weather. Over a four-day period from the 6th to the 9th we received 10.8 inches of snowfall. This marked our first snowfall of the season, nearly three weeks later than normal.

From there, we again entered a relatively mild period with dry conditions that lasted 17 days. Finally, on the 27th, we received another nice shot of snow (3.4 inches). The weather then became calm and pleasant for the Thanksgiving weekend.

For the month of November 2024, Thornton’s average temperature came in at 37.9 degrees. This was a good bit cooler than our running 18-year average for November of 39.6 degrees. Temperatures ranged from a high of 68.7 degrees on the 23rd down to a low of 15.3 degrees on the morning of the 28th.

Out at Denver International Airport where Denver’s official measurements are taken, the Mile High City saw an average temperature for the month of 38.2 degrees. This was below their long term November average of 39.4 degrees.

In terms of precipitation, between rain and melted snow, Thornton recorded a very healthy 1.76 inches for the month. This was far above our running average for November of 0.54 inches. It was, in fact, the wettest November we have recorded in 18 years.

The Mile High City saw 1.98 inches in their bucket, mainly due to higher snowfall out at the airport. This was well above Denver’s long term November average of 0.64 inches and was the 5th wettest November ever recorded in Denver.

As previously mentioned, snowfall was quite abundant. Thornton recorded 14.2 inches, more than double our 18-year November average of 6.2 inches. This made November 2024 the third snowiest November in our books over that period.

Denver bested us on the snowfall front with a whopping 23.3 inches at the airport. This was far above their long-term November average of 7.3 inches. It also put November 2024 into Denver’s record books as the 4th snowiest November ever recorded.

Click here to view Thornton’s complete November 2024 climate summary report.

Thornton, Colorado's November 2024 Precipitation Summary. (ThorntonWeather.com)
Thornton, Colorado’s November 2024 Precipitation Summary. (ThorntonWeather.com)
Climatology, Thornton Weather

Thornton’s December 2024 preview: Winter arrives, typically with cold and snow

Thornton, Colorado's December Weather Preview

Recent months have, overall, been mostly warmer and drier than normal.  Last month we finally got a break with cooler temps and a healthy dose of snow.  What will December hold for us?

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 31.2 degrees (1991 – 2020 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 8.0 inches of the white stuff.

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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Climatology, National Weather, Thornton Weather

Weather and Election Day 2024: Will Mother Nature play a role in the outcome?

Weather and Elections - Does Mother Nature play a role in determining the outcome?
Weather and Elections – Does Mother Nature play a role in determining the outcome?

We oftentimes hear about how weather can affect voter turnout but is there truly a link?  If there is, who does it benefit – Republicans or Democrats?  Studies seem to indicate that what might be thought of as an urban myth is indeed true and could in fact play a role in 2024.

In 2005, political science researchers Brad Gomez, Thomas Hansford and George Krause completed the first comprehensive study on the correlation between weather and voter turnout.  Their paper, “The Republicans Should Pray for Rain:  Weather, Turnout, and Voting in U.S. Presidential Elections” confirmed the conventional wisdom that weather does affect voter turnout, bad weather benefits Republicans and most interestingly, two presidential elections in the last 60 years may have had different results had the weather been different.

Looking back at presidential elections from 1948 to 2008, the study takes into account the weather in 3,000 U.S. counties.  They in turn looked at key areas of the nation and how weather, good and bad, affected voter turnout.  In the end, the study determined that precipitation is the key weather condition to affect voter turnout.

Continue reading Weather and Election Day 2024: Will Mother Nature play a role in the outcome? →

Climatology, Thornton Weather

October 2024 weather recap: The warmest, second driest October of the past 18 years

Thornton, Colorado's October 2024 Temperature summary. (ThorntonWeather.com)
Thornton, Colorado’s October 2024 Temperature summary. (ThorntonWeather.com)

Mild and dry were the keywords for Thornton for October 2024. The month came in as the warmest and the second driest October of the past 18 years.

While the month lacked any sort of drama in the way of storms, it was most notable for the temperatures. We saw our last 90-degree day of the year on October 2nd and the first 16 days of the month saw 10 days with 80 degree or warmer readings. We didn’t see our first freezing temperature of the season until the 25th of the month, more than two weeks later than normal.

The latter half of the month did cool some but mercury readings remained above normal on most days. Overall, 27 of the 31 days of the month saw above average high temperatures.

Precipitation for the month was meager to say the least. It wasn’t until the 30th that we saw any and even then, it was a paltry 0.03 inches. No snow was recorded.

October 2024 Climate Location Comparison (© ThorntonWeather.com)
October 2024 Climate Location Comparison (© ThorntonWeather.com)

Thornton’s average temperature for the month came in at 56.1 degrees. That was far above the 50.0 degree 18-year running average for October in Thornton. It also goes into the books as our warmest October over that period, besting the 55.8 degree average of October 2016.

Temperatures ranged from a high of 90.3 degrees on the 2nd of the month down to a low of 29.2 degrees on the morning of the 31st.

The Mile High City, as officially measured at Denver International Airport, was even warmer. Their October average temperature came in at 59.1 degrees. That was far above Denver’s long term October average of 51.1 degrees. The month goes into the Denver weather record books as the second warmest on record with October 1950 holding on as the warmest (59.9 degrees).

Temperatures at the airport ranged from a high of 89 degrees on the 2nd to a low of 24 degrees on the 31st.

As noted above, precipitation was almost non-existent with only 0.03 inches recorded. This was far below the 0.92 inch running average Thornton has seen in October over the past 18 years. October 2024 goes into the books as the second driest October during that time, second only to October 2021 (0.02”).

Out at the airport, Denver saw 0.09 inches of precipitation, all coming on the 18th of the month. This was far short of the 0.99 inches the Mile High City averages in October. That makes October 2024 the 11th driest October ever recorded in Denver.

Over the past 18 years, Thornton has averaged 3.8 inches of snow in October. This year, none was recorded. That is not, however, all that unusual as seven other Octobers over the past 18 years saw no snow as well.

Similarly, out at DIA, Denver saw no snowfall for the month. This ties with 20 other Octobers since 1882 in Denver with no snow. On average, Denver records 4.1 inches during the month.

Click here to view Thornton’s complete October 2024 climate summary report.

Thornton, Colorado's October 2024 Precipitation Summary. (ThorntonWeather.com)
Thornton, Colorado’s October 2024 Precipitation Summary. (ThorntonWeather.com)
Climatology, Thornton Weather

November 2024 preview: The transition to winter begins

 

November

The weather during the month of November in Denver metro area can offer just about anything.  While it is normally a quiet month, it can be prone to extremes.

November has historically been one of Denver’s snowiest months and major snowstorms are not entirely uncommon.  However conditions can also be quite dry.

Temperatures during the month continue to cool as we get closer to winter and by the end of the month the low temperatures routinely dip to 20 degrees or below.  At times it can in fact bring conditions more like what we see in January.

Get all the details on November’s weather and what we can expect in our complete preview here.

Climatology, Thornton Weather

Thornton and Denver record their first freezing temperature of the season

Cold thermometer

Better late than never? Unseasonably warm and dry conditions have been the hallmark of October so far. Today, we finally got a taste of the temperatures we normally expect to see.

Just before sunrise, both Thornton and Denver saw temperatures drop to 32 degrees marking the first freeze of the season. This comes more than 2 1/2 weeks after the average date of the first freeze in Denver of October 7th.

With that reading the book, we do continue to wait for our first snow of the season. That may come early to mid-week next week.

Climatology, Thornton Weather

September 2024 weather recap: Thornton sees its warmest September of the past 17 years

Thornton, Colorado's September 2024 temperature summary. (ThorntonWeather.com)
Thornton, Colorado’s September 2024 temperature summary. (ThorntonWeather.com)

Mother Nature can be so fickle. While September brings the start of autumn, she was intent on keeping summer rolling along and in doing so, delivered mercury readings well above normal.

The month was a calm one, lacking much of any kind of drama beyond the temperatures. We started out very warm and dry for the first three days then, finally, a little bit of relief arrived. Temperatures cooled a bit and we received a nice shot of rain on the 4th and 5th.

For the next two weeks, dry conditions dominated with no precipitation. Over the period temperatures remained well above normal.

Finally, on the 21st, we saw some relief and temperatures on the 21st and 22nd were only in the 60s. We also received a welcome shot of rain totaling 0.81 inches.

Temperatures rebounded on the 23RD and dry weather continued through the end of the month.

September 2024 Climate Location Comparison (© ThorntonWeather.com)
September 2024 Climate Location Comparison (© ThorntonWeather.com)

In the end, Thornton saw an average temperature for September 2024 of 67.9 degrees. This was far above the running 17-year average for the month of 64.2. In fact, it was Thornton’s warmest September over the period. Temperatures in Thornton ranged from a high of 93.1 degrees on the 3rd down to a low of 42.7 degrees on the 23rd.

For Denver, as measured at Denver International Airport, the month was a good bit warmer recording an average of 70.0 degrees. This too was far above the month’s average of 64.8 degrees. Further, it put September 2024 into the books as the Mile High City’s warmest September on record.

Thornton really only saw two rain events but both were pretty decent ones, dropping 1.26 inches into the rain bucket for the month. That was a bit below our September average of 1.48 inches.

Denver recorded very similar numbers with 1.24 inches of precipitation. This was just shy of the Mile High City’s September average of 1.35 inches.

Neither Thornton nor Denver recorded any snow during September 2024.

Click here to view Thornton’s complete September 2024 climate summary report.

Thornton, Colorado's September 2024 precipitation summary. (ThorntonWeather.com)
Thornton, Colorado’s September 2024 precipitation summary. (ThorntonWeather.com)
Climatology, Thornton Weather

Thornton’s October 2024 preview: Generally calm conditions with our first freeze and snow

Thornton, Colorado October weather preview.With the first full month of fall here, October usually brings one of the quietest weather months in the Denver area with plenty of mild, sunny days and clear, cool nights.

October is historically the second sunniest month and conditions are generally calm.

However we also will usually see our first taste of winter during the month with the first freeze and first snowfall of the season.  Temperatures as well will start to drop and by the end of the month the average nighttime lows are below freezing.

For complete details on our historical October weather and what we can expect in the coming month, read our complete October weather preview here.

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