Preview of Thornton's October Weather - Fall is Here

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.

The month actually has our second highest amount of sunshine with 72 percent with September having the most with 74 percent. Interestingly enough, the month following, November, is one of the lowest sunshine months with only 64 percent. Typically October brings our first real taste of winter with the first freeze on average coming on the 7th of the month and the first snow on the 15th of the month.

Average temperatures in October steadily drop throughout the month. On the first we average 72 degree highs but by the 31st that drops to 59 degrees. October also sees our average low temperatures start to reach below freezing as well. At the start of the month we will average 42 degrees as the low temperature but by the end of the month the mercury dips to 31 degrees. This truly begins the sign that winter is approaching.

Temperatures can run from one extreme to the next during October. The record high temperature is 90 degrees which was set on October 1, 1892. By contrast, the coldest temperature was 2 degrees below zero set on October 29th, 1917. Those temperature swings can occur in a very short period of time as well. On October 2, 1969 Denver enjoyed a balmy high temperature of 85 degrees. Over the next two days though on the 3rd and 4th, 15 inches of snow fell in the area. Another example of those changes happened in 1991 when on the 16th we reached 89 degrees then had record low temperatures of 7 degrees on the 30th and 10 degrees on the 31st.

October on average is our 5th driest month, averaging 0.97 inches of precipitation (rain and snow melt combined) with 4.1 inches of snow on average during the month. Precipitation overall can range from a trace to a record of 4.17 inches of precipitation in 1969. 1934 was the driest October on record with only a trace recorded. In terms of snow, there have been many years when no snow or only a trace of snow was recorded – in 36 out of the last 126 years that was the case.

Record setting precipitation was the highlight of October 2007. In the 24 hour period between October 13 and 14, 2.65 inches of precipitation was recorded at DIA. This broke the previous 24 hour record of 2.58 inches set on the 12th and 13th of the month in 1892. The previous daily record of 2.11 inches in 1892 was also broken with 2.48 inches of precipitation on the 13th.

What is probably one of Denver’s most famous snowstorms occurred in October and was seen live on national television. On Monday, October 15th, 1984 the Denver Broncos faced off against the Green Bay Packers at Mile High Stadium in what came to be known as the “Bronco Blizzard.” The storm gradually intensified during the game and by the end of the game the field was covered with four inches of snow. By the time the storm was over, over a foot of snow had fallen in most of the metro area. The weather proved to be the deciding factor in the game as the Broncos recovered two back to back Packer fumbles and returned them for touchdowns, winning the game 17-14. Ski areas rejoiced in their “white gold” and saw a surge in reservations from out of state as the nation watched this tremendous storm unfold on television.

October 1997 saw tremendous snowfall and ended up being the 3rd snowiest October in Denver history. From October 24th to 25th 19.1 inches had fallen during a 24 hour period, setting a new October record. By the time the storm ended, 21.9 inches of snow had fallen at Stapleton International Airport over the two day period.

Looking back at October 2010

Following on what was a "top 10" warmest and driest September last year, October 2010 tried to follow suit but fell short of achieving record status.  Nevertheless, the month was considerably warmer and drier than normal.

In terms of temperature the month ranked as the 11th warmest fall just 0.1 degree short of top 10 status.  The average temperature was 55.3 degrees; a considerable 4.3 degrees above normal.  Temperatures ranged from a high of 85 degrees on the 3rd down to a low of 20 on the 28th.  In all there were only two days when the mercury dipped to freezing or below; seven days below the normal nine we receive.

Thornton was quite a bit cooler overall than Denver as we had an average temperature of 52.7 degrees.  Highs ranged from 84 degrees on the 4th down to 23.3 degrees on the 28th.

We suffered through another dry month which did spark a couple of wildfires.  A mere 0.54 inch of precipitation was recorded at the official monitoring site at Denver International Airport.  This was just barely more than half of the normal of 0.99 inch.  Most of the precipitation fell in the form of rain on the 12th when 0.34 inch was recorded. 

Here in Thornton we were a bit wetter having recorded 0.73 inch of precipitation during the month.

For the first time since 2003 no snow was recorded in Denver in October.  This was only the 15th time since 1882 that has happened.  On average we expect to receive 4.1 inches of the white stuff.

Outlook for October 2011

The long term National Weather Service outlook calls for above normal temperatures and near normal precipitation.

For More Information

Temperature Normals and Extremes for October

Monthly Temperature, Rainfall and Snowfall Extremes for October

OCTOBER AVERAGE STATISTICS * Normals & Means, 1981 - 2010
TEMPERATURE
AVERAGE HIGH	65.3
AVERAGE LOW	36.6
MONTHLY MEAN	50.9
DAYS WITH HIGH 90 OR ABOVE	0
DAYS WITH HIGH 32 OR BELOW	0 * (LESS THAN 1)
DAYS WITH LOW 32 OR BELOW	9
DAYS WITH LOWS ZERO OR BELOW	0
PRECIPITATION
MONTHLY MEAN	0.97 INCHES
DAYS WITH MEASURABLE PRECIPITATION	5
AVERAGE SNOWFALL	4.1 INCHES
DAYS WITH 1.0 INCH OR MORE SNOWFALL	1
MISCELLANEOUS OCTOBER AVERAGES
HEATING DEGREE DAYS	440
COOLING DEGREES DAYS	5
WIND SPEED (MPH)	7.8 MPH
WIND DIRECTION	SOUTH
DAYS WITH THUNDERSTORMS	1
DAYS WITH DENSE FOG	1
PERCENT OF SUNSHINE POSSIBLE	72
OCTOBER EXTREMES
RECORD HIGH	90 ON 10/01/1892
RECORD LOW	-2 ON 10/29/1917
WARMEST	59.9 IN 1950
COLDEST	39.0 IN 1969
MAXIMUM 24 HOUR RAIN	2.58 INCHES IN 1892 (12-13)
DRIEST	TRACE IN 1934
WETTEST	4.17 INCHES IN 1969
MAXIMUM 24 HOUR SNOWFALL	19.1 INCHES IN 1997 (24 - 25) (BLIZZARD OF 1997)
SNOWIEST	31.2 INCHES IN 1969
LEAST SNOWIEST	0 (14 YEARS)

* Historical weather statistics gathered from the National Weather Service's Denver / Boulder forecast office data archives.