Typically November is a quiet weather month with plenty of nice, fall days but it can also turn wet with plenty of snow and moisture. Just like Forest Gump’s proverbial box of chocolates, you never quite know what you are going to get.
Looking into the weather history books, we see that November is actually Denver’s second snowiest month, second only to March (April is third). Historically we average 10.7 inches of snow during the month.
One little known fact… November is the area’s least sunny month, tying with May with only 64 percent sunshine. September is the sunniest month with sunshine 74 percent of the time.
Get all the details on Denver’s November weather including a look back through history, a recap of last year and the statistics in our November weather preview.
August 2011 brought record-setting heat to Denver.
You didn’t need to know the statistics to be well aware that August was unusually warm and dry in Thornton and Denver. The month saw little precipitation and record setting temperatures became commonplace, particularly in the latter half of the month.
For moisture, Denver recorded a mere 0.30 inch in the rain bucket at Denver International Airport. This was 1.27 inches below the normal of 1.57 inches. The month barely missed making the list of top 10 driest Augusts by only 0.02 inch.
Afternoon thunderstorms were seen 12 times at DIA but only one brought measurable precipitation. The storms were typically high-based and yielded little more than wind.
Thornton followed DIA’s lead with little precipitation as we only saw 0.27 inch during the month.
Temperatures were the real weather story for August 2011 as rather than seeing cooler temperatures through the month like normal, the mercury stayed exceedingly high.
Overall DIA saw an average temperature of 77.0 degrees making it the hottest August on record. This surpassed the previous record August from 1937 when 76.8 degrees was seen. The month also went into the record books as the sixth warmest month ever recorded in Denver.
Temperatures ranged from a high of 99 degrees on the 25th down to a low of 55 degrees on the 20th. Through August 31st, Denver had seen 71 consecutive days of 80 degrees or warmer weather. This easily bested the previous longest streak of 59 days set in 2002.
Seven individual temperature records were set during the month. These included a tied record high on the 18th of 98 degrees last set in 1986; the 23rd tied the record high of 98; the 24th set a new record high for the date of 98 degrees; the 25th set a new record high of 99 degrees; the 28th set a record high of 96 degrees; the 28th saw a record high minimum of 67 degrees; the 31st tied the record high of 98 degrees.
Here in Thornton we were certainly hot but not nearly as much so as DIA. We recorded an average temperature of 74 degrees. Our warmest reading was 96.2 degrees and our coolest was 54. In all we saw 20 days with temperatures of 90 degrees or warmer.
While the high temperatures were notable, DIA benefits from later arrival of the typical afternoon thunderstorms due to its location further east of the rest of Denver. This certainly aided in the airport recording higher temperatures than anywhere else in the metro area. For more on that story, check out the Denver Weather Examiner.
CLIMATE REPORT...CORRECTED
NATIONAL WEATHER SERVICE BOULDER, CO
430 PM MDT FRI SEP 2 2011
...................................
...THE DENVER CO CLIMATE SUMMARY FOR THE MONTH OF AUGUST 2011...
CLIMATE NORMAL PERIOD 1981 TO 2010
CLIMATE RECORD PERIOD 1872 TO 2011
WEATHER OBSERVED NORMAL DEPART LAST YEAR'S
VALUE DATE(S) VALUE FROM VALUE DATE(S)
NORMAL
................................................................
TEMPERATURE (F)
RECORD
HIGH 105 08/08/1878
LOW 40 08/26/1910
08/25/1910
08/24/1910
HIGHEST 99 08/25 105 -6 97 08/22
LOWEST 55 08/20 40 15 47 08/17
AVG. MAXIMUM 92.7 87.2 5.5 88.6
AVG. MINIMUM 61.3 57.9 3.4 59.0
MEAN 77.0 72.5 4.5 73.8
DAYS MAX >= 90 22 11.5 10.5 12
DAYS MAX <= 32 0 0.0 0.0 0
DAYS MIN <= 32 0 0.0 0.0 0
DAYS MIN <= 0 0 0.0 0.0 0
PRECIPITATION (INCHES)
RECORD
MAXIMUM 5.85 1979
MINIMUM 0.02 1924
TOTALS 0.30 1.57 -1.27 1.05
DAILY AVG. 0.01 0.05 -0.04 0.03
DAYS >= .01 3 8.6 -5.6 6
DAYS >= .10 1 4.3 -3.3 3
DAYS >= .50 0 1.2 -1.2 1
DAYS >= 1.00 0 0.3 -0.3 0
GREATEST
24 HR. TOTAL 0.27 08/03 TO 08/03 0.68 08/01/10 TO 08/01/10
SNOWFALL (INCHES)
RECORDS
TOTAL 0.0 NO SNOW EVER RECORDED IN AUGUST
TOTALS 0.0 NO SNOW EVER RECORDED IN AUGUST
DEGREE_DAYS
HEATING TOTAL 0 5 -5 0
SINCE 7/1 0 11 -11 3
COOLING TOTAL 382 244 138 280
SINCE 1/1 863 688 175 762
FREEZE DATES
RECORD
EARLIEST 09/08/1962
LATEST 06/08/2007
EARLIEST 10/07
LATEST 05/05
..................................................
WIND (MPH)
AVERAGE WIND SPEED 8.8
RESULTANT WIND SPEED/DIRECTION 3/202
HIGHEST WIND SPEED/DIRECTION 39/180 DATE 08/31 38/190 08/12
HIGHEST GUST SPEED/DIRECTION 48/200 DATE 08/31 45/340 08/12
08/16
SKY COVER
POSSIBLE SUNSHINE (PERCENT) MM (NO LONGER RECORDED)
AVERAGE SKY COVER 0.50
NUMBER OF DAYS FAIR 4
NUMBER OF DAYS PC 26
NUMBER OF DAYS CLOUDY 1
AVERAGE RH (PERCENT) 41
WEATHER CONDITIONS. NUMBER OF DAYS WITH
THUNDERSTORM 0 MIXED PRECIP 0
HEAVY RAIN 1 RAIN 1
LIGHT RAIN 8 FREEZING RAIN 0
LT FREEZING RAIN 0 HAIL 0
HEAVY SNOW 0 SNOW 0
LIGHT SNOW 0 SLEET 0
FOG 4 FOG W/VIS <= 1/4 MILE 1
HAZE 5
- INDICATES NEGATIVE NUMBERS.
R INDICATES RECORD WAS SET OR TIED.
MM INDICATES DATA IS MISSING.
T INDICATES TRACE AMOUNT.
August 2011 goes into the record books as the hottest August ever.
As August 2011 came to a close and the numbers were crunched, they revealed what we already knew – it was one hot month! In fact, in the final tally Denver tied or set 10 different records during the month.
From the National Weather Service, here is the list of records:
Denver’s record setting August 2011 – From the National Weather Service:
August 2011 hottest Denver August with average temperature 77.0 degrees. Previous record 76.8 degrees set in 1937.
August 2011 became the 6th hottest Denver month. Hottest was 77.8 during July 1934.
71 consecutive days above 80 degrees through August 31st. Previous streak record 59 days set in 2002.
Tied most August 90 degree days with 22. Tied with 1995 and 1960.
18th – tied record high 98 last 1986
23rd – tied record high 98 last 2009
24th – record high 98 old 97 in 1936
25th – record high 99 old 96 in 1913
28th – record high 96 old 94 last 1969
28th – record high minimum temperature 67 old 66 last 2010
31st – tied record high 98 last 1960
How did Thornton compare?
Here in Thornton we were a bit cooler than what Denver’s official measurements at DIA recorded. This is in large part due to our location further to the west.
When the typical afternoon cloud cover and thunderstorms develop in the summer, it can take more than an hour for those conditions to reach DIA. As a result the station gets the benefit of a longer period of daytime heating. This works in Thornton’s favor as we stay a bit cooler.
For us, our overall average temperature for the month was 74.0 degrees – a full three degrees cooler than DIA. That doesn’t mean it wasn’t hot for us as we recorded 20 days with 90 degree or hotter weather and every day saw 80 degrees or higher.
Are the Denver weather records really valid? Check out the stories from Examiner.com below for why they may not be.
As temperatures start to drop, September 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.
Normal highs on the first of the month are 82 degrees with a low of 53. By the end of the month we see those high temperatures drop to an average of 73 and the lows get to a chilly 42. Overall the month averages 63.4 degrees.
July 2011 was much wetter and slightly warmer than normal. (ThorntonWeather.com)
Historically July is a pretty busy month in terms of weather as thunderstorms are very common. July 2011 lived up to the month’s reputation as the middle of the month saw a seemingly endless stream of heavy, wet thunderstorms. This was followed by a string of 90 degree and warmer days that approached record setting territory.
The big story for the month was the precipitation as there was a lot of it. DIA saw sixteen thunderstorms during July, five more than normal. The official Denver monitoring at the airport recorded 3.41 inches of rain which was well above the normal of 2.16 inches. The measurement fell just shy of making the list of top 10 wettest July’s on record.
The station at DIA however lived up to its reputation as under-reporting rainfall as compared to locations closer to downtown. In fact, a station the old Stapleton site recorded 6.54 inches. Here in Thornton 5.51 inches fell into our rain bucket.
One precipitation record was set during the month when 1.03 inches of rain fell on the 13th. This easily bested the previous 24 hour record for the date of 0.45 inch set in 1993.
Temperatures for the month were considerably above normal but fell short of ‘top 10’ status. The average temperature for the month, as recorded at DIA, was 75.9 degrees. This was 2.5 degrees above the normal of 73.4.
The warmest temperature of the month occurred on the Fourth of July when the mercury climbed to 99 degrees. On the opposite end, 56 degrees on the 1st of the month was the coldest reading.
In all, 20 days saw temperatures at or above 90 degrees during July 2011; five more than normal. July 15th started a string of 18 consecutive days of 90 degree or warmer high temperatures. That streak will go into the books as tying for the second longest in history.
Thornton, like most other places in the metro area, was not near as warm. Our average temperature was 73.8 degrees, right near normal. Our warmest temperature occurred on the 4th as well and matched Denver’s mark of 99 degrees. The mercury dipped to 53.6 degrees on the 1st and was our coldest temperature.
...THE DENVER CO CLIMATE SUMMARY FOR THE MONTH OF JULY 2011...
CLIMATE NORMAL PERIOD 1971 TO 2000
CLIMATE RECORD PERIOD 1872 TO 2011
WEATHER OBSERVED NORMAL DEPART LAST YEAR'S
VALUE DATE(S) VALUE FROM VALUE DATE(S)
NORMAL
................................................................
TEMPERATURE (F)
RECORD
HIGH 105 07/20/2005
LOW 42 07/04/1903
07/31/1873
HIGHEST 99 07/31 105 -6 102 07/17
07/04
LOWEST 56 07/01 42 14 53 07/09
07/05
07/04
AVG. MAXIMUM 91.1 88.0 3.1 89.3
AVG. MINIMUM 60.7 58.7 2.0 59.5
MEAN 75.9 73.4 2.5 74.4
DAYS MAX >= 90 20 15.0 5.0 18
DAYS MAX <= 32 0 0.0 0.0 0
DAYS MIN <= 32 0 0.0 0.0 0
DAYS MIN <= 0 0 0.0 0.0 0
PRECIPITATION (INCHES)
RECORD
MAXIMUM 6.41 1965
MINIMUM 0.01 1901
TOTALS 3.41 2.16 1.25 3.70
DAILY AVG. 0.11 0.07 0.04 0.12
DAYS >= .01 11 9.3 1.7 13
DAYS >= .10 7 MM MM 5
DAYS >= .50 2 MM MM 2
DAYS >= 1.00 2 MM MM 2
GREATEST
24 HR. TOTAL 1.08 07/12 TO 07/13 1.84 07/04/10 TO 07/04/10
SNOWFALL (INCHES)
RECORDS
TOTAL 0.0 NONE EVER RECORDED IN JULY
TOTALS 0.0 0.0
DEGREE_DAYS
HEATING TOTAL 0 1 -1 3
SINCE 7/1 0 1 -1 3
COOLING TOTAL 346 261 85 303
SINCE 1/1 481 422 59 482
FREEZE DATES
RECORD
EARLIEST 09/08/1962
LATEST 06/08/2007
EARLIEST 10/07
LATEST 05/05
......................................................
WIND (MPH)
AVERAGE WIND SPEED 9.5 9.1
RESULTANT WIND SPEED/DIRECTION 3/181 MM
HIGHEST WIND SPEED/DIRECTION 51/210 DATE 07/13 41 07/30/10
HIGHEST GUST SPEED/DIRECTION 68/300 DATE 07/14 48 07/30/10
SKY COVER
POSSIBLE SUNSHINE (PERCENT) MM
AVERAGE SKY COVER 0.50
NUMBER OF DAYS FAIR 6
NUMBER OF DAYS PC 22
NUMBER OF DAYS CLOUDY 3
AVERAGE RH (PERCENT) 50
WEATHER CONDITIONS. NUMBER OF DAYS WITH
THUNDERSTORM 0 MIXED PRECIP 0
HEAVY RAIN 4 RAIN 6
LIGHT RAIN 17 FREEZING RAIN 0
LT FREEZING RAIN 0 HAIL 4
HEAVY SNOW 0 SNOW 0
LIGHT SNOW 0 SLEET 0
FOG 5 FOG W/VIS <= 1/4 MILE 0
HAZE 4
- INDICATES NEGATIVE NUMBERS.
R INDICATES RECORD WAS SET OR TIED.
MM INDICATES DATA IS MISSING.
T INDICATES TRACE AMOUNT.
Hot or cold: Denver's problematic weather records. (Denver Weather Examiner)
Does a move of 12 miles make a difference in what type of weather is seen in Colorado? Longtime residents know that our weather can vary greatly over short distances and this has many questioning the placement of Denver’s official weather monitoring station.
From 1871 to 1949 Denver’s weather was recorded at the National Weather Service’s office in downtown Denver. In January 1950 a move was made to Stapleton International Airport.
As that facility aged Denver opened Denver International Airport on the plains northeast of Denver in 1995. The weather service followed suit and moved the Mile High City’s official weather station the 12 miles to DIA.
Since that time, many weather watchers have noticed problems – DIA is consistently warmer and drier than the old site at Stapleton. Further, its remote location gives conditions far from where most people in Denver live and thus doesn’t accurately represent what they are experiencing.
Even bigger issues arise when comparing weather data taken today with measurements previously recorded at Stapleton or downtown. The different microclimates of the sites are so different that it becomes much like comparing apples and oranges.
This was recently made evident with the string of 90 degree or warmer days we put together. If you went by the station at DIA, the streak lasted 18 days putting in a three way tie for the second longest streak in Denver history. However, no monitoring station closer to the city was as warm.
Further, while July was certainly a wet month, DIA’s precipitation measurements fell far short of most other locations.
Amid concerns about a warming climate, can we trust the measurements at DIA? How is it possible to compare the weather today with historical weather when there is such a large discrepancy?
We recently tackled this topic on the Denver Weather Examiner and the conclusion is obvious – It simply is impossible to correlate current weather records with Denver’s historical ones. Further, the National Weather Service seems intent on ignoring the issue.
Thornton’s June 2011 weather was a relatively typical one with average temperatures but also with above normal precipitation. The month also signifies the official end of the 2010 to 2011 snow season which was absolutely dismal.
In terms of temperatures Denver saw an average temperature for the month of 68.2 degrees. This was just a bit above the normal of 67.6 degrees. Temperatures ranged from a high of 96 degrees on the 28th and 29th down to a low of 45 degrees on the 10th. DIA recorded seven days with 90 degrees or higher temperatures which is one above normal. No temperature records were set for the month.
Here in Thornton we came quite close to mirroring Denver’s official temperatures. Our average temperature was 68.1 degrees with the highest mercury reading of 96.4 degrees coming on the 29th. The lowest temperature in Thornton came on the 3rd at 45.4 degrees.
Precipitation for the month was above normal as DIA’s rain bucket recorded 2.43 inches. This was 0.87 inch above the normal of 1.56 inch and the second month in a row with above normal precipitation. In all, eight days had measurable precipitation and DIA reported thunderstorms on 10 days which is average.
One precipitation record was set during the month when 1.05 inches of rain was recorded on the 20th. This beat the old record for the date of 0.50 inch set in 1939.
We were quite a bit drier in Thornton as our precipitation for the month fell below the Denver normals. We recorded 1.14 inches for the month with the majority of that, 0.87 inch, falling on the 20th.
Denver’s snow season runs from July 1 to June 30 and with the end of the 2010 to 2011 season the numbers show just how poorly we faired in terms of snowfall. The Mile High City recorded a mere 22.8 inches of the white stuff at DIA. This is a whopping 38.9 inches below the normal of 61.5 inches. The season will go into the record books as the second least snowiest snow season since Denver began keeping records in 1882.
Here in Thornton we did not fare any better than Denver on the snowfall front. Our season wrapped up with a dismal 21.2 inches.
Denver, Colorado June 2011 Climate Summary
CLIMATE NORMAL PERIOD 1971 TO 2000
CLIMATE RECORD PERIOD 1872 TO 2011
WEATHER OBSERVED NORMAL DEPART LAST YEAR'S
VALUE DATE(S) VALUE FROM VALUE DATE(S)
NORMAL
................................................................
TEMPERATURE (F)
RECORD
HIGH 104 06/26/1994
LOW 30 06/02/1951
HIGHEST 96 06/29 104 -8 99 06/25
06/28
LOWEST 45 06/10 30 15 47 06/23
06/18
06/14
06/12
AVG. MAXIMUM 83.3 82.1 1.2 84.1
AVG. MINIMUM 53.0 53.0 0.0 53.6
MEAN 68.2 67.6 0.6 68.9
DAYS MAX >= 90 7 6.3 0.7 10
DAYS MAX <= 32 0 0.0 0.0 0
DAYS MIN <= 32 0 0.0 0.0 0
DAYS MIN <= 0 0 0.0 0.0 0
PRECIPITATION (INCHES)
RECORD
MAXIMUM 4.96 1882
MINIMUM T 1890
TOTALS 2.43 1.56 0.87 1.60
DAILY AVG. 0.08 0.05 0.03 0.05
DAYS >= .01 8 8.7 -0.7 5
DAYS >= .10 4 MM MM 3
DAYS >= .50 2 MM MM 2
DAYS >= 1.00 1 MM MM 0
GREATEST
24 HR. TOTAL 1.55 06/19 TO 06/20 1.25 06/11 TO 06/12
SNOWFALL (INCHES)
RECORDS
TOTAL 0.4 1919
TOTALS 0.0 T
DEGREE_DAYS
HEATING TOTAL 26 60 -34 38
SINCE 7/1 5707 6128 -421 6441
COOLING TOTAL 126 136 -10 163
SINCE 1/1 135 161 -26 179
FREEZE DATES
RECORD
EARLIEST 09/08/1962
LATEST 06/08/2007
EARLIEST 10/07
LATEST 05/05
.................................................
WIND (MPH)
AVERAGE WIND SPEED 10.4
RESULTANT WIND SPEED/DIRECTION 3/148
HIGHEST WIND SPEED/DIRECTION 48/190 DATE 06/29
HIGHEST GUST SPEED/DIRECTION 72/200 DATE 06/29
SKY COVER
POSSIBLE SUNSHINE (PERCENT) MM
AVERAGE SKY COVER 0.50
NUMBER OF DAYS FAIR 7
NUMBER OF DAYS PC 21
NUMBER OF DAYS CLOUDY 2
AVERAGE RH (PERCENT) 45
WEATHER CONDITIONS. NUMBER OF DAYS WITH
THUNDERSTORM 0 MIXED PRECIP 0
HEAVY RAIN 3 RAIN 2
LIGHT RAIN 10 FREEZING RAIN 0
LT FREEZING RAIN 0 HAIL 1
HEAVY SNOW 0 SNOW 0
LIGHT SNOW 0 SLEET 0
FOG 4 FOG W/VIS <= 1/4 MILE 0
HAZE 6
- INDICATES NEGATIVE NUMBERS.
R INDICATES RECORD WAS SET OR TIED.
MM INDICATES DATA IS MISSING.
T INDICATES TRACE AMOUNT.
Our normally widely varied weather settles into a somewhat standard pattern during the month of July. The mercury climbs each day in what is our hottest month and thunderstorms become very common during the afternoon and evening hours.
The average monthly high temperature for July is 88 degrees and can oftentimes get much higher than that. In fact, the record high temperature for all but seven days during the month are at or above 100 degrees.
Afternoon thunderstorms occur on average every three days during July. These events can be extreme and are known to bring heavy rains and damaging wind and hail.
May 2011 will go into the books as the 11th coldest and 5th wettest May on record in Denver.
There was little doubt that last month was a wet one and now that May 2011 has come to a close we can see that it certainly was. In fact, it was one of the wettest Mays on record and also one of the coldest.
Up until the last few days of the month it looked like we were going to make the top 10 list for coldest Mays on record. But, thanks to a few near-normal days, our average temperature for the month ended at 53.1 degrees. This fell just short of the number 10 spot on the list of 53.0 degrees recorded in 1950.
Nevertheless the month’s average temperature was 4.1 degrees below the normal of 57.2 degrees. Our warmest temperature of the month of 86 degrees was recorded on both the 7th and the 8th and those were two of only three days with temperatures above 80 degrees.
On the low end the coldest temperature was seen on the 5th when the mercury dropped to 28 degrees. This is also the last time we saw a temperature at or below freezing and will almost certainly be the last for the 2010 – 2011 winter season. Coincidentally, May 5th is the average date of our last freeze so we were right on the mark this year.
Here in Thornton we saw an average temperature of 52.9 degrees. Our warmest temperature was 86.8 degrees and our coldest 29.2 degrees.
May brought an abundance of precipitation eliciting many jokes about Denver having swapped locations with Seattle. In all, 4.79 inches of moisture was recorded at Denver International Airport during the month putting it in the books as the 7th wettest May on record. This was 2.47 inches above the May average of 2.32 inches.
Here in Thornton we recorded nearly an inch of precipitation more than what was recorded at DIA. ThorntonWeather.com saw 5.67 inches fall into our bucket for the month.
On average we record 1.3 inches of snow in May but last month continued the trend we saw all winter of a severe lack of snowfall. Only 1.0 inch of the white stuff was recorded at DIA and most of the metro area saw nothing during the month (including Thornton).
Given that it is highly unlikely June will bring any snow to Denver, the 2010 to 2011 season will wrap up with only 22.8 inches of snow – far below the 61.7 inches average. This will put the season into the history books as the 2nd least snowiest snow season on record. Only the 1888 to 1889 season saw less with 21.3 inches.
Thornton actually fared worse throughout the entire snow season and we are going to wrap it up with a paltry 21.2 inches.
June is historically Denver’s severe weather month and severe thunderstorms, tornadoes and hail are notorious visitors to Denver and across eastern Colorado during the month.
In fact, over 40 percent of the tornadoes that occur in Colorado are observed in June and these are typically the most destructive of the year. Thornton of course knows this fact well as this year we celebrate the 30th anniversary of the infamous Thornton tornado of June 3, 1981.
Severe thunderstorms have also caused major property damage across the Front Range during the month. Just last year hail the size of golf balls caused damage across parts of central and northeastern Thornton.
Typically November is a quiet weather month with plenty of nice, fall days but it can also turn wet with plenty of snow and moisture. Just like Forest Gump’s proverbial box of chocolates, you never quite know what you are going to get.
As temperatures start to drop, September 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.
Thornton’s June 2011 weather was a relatively typical one with average temperatures but also with above normal precipitation. The month also signifies the official end of the 2010 to 2011 snow season which was absolutely dismal.
June is historically Denver’s severe weather month and severe thunderstorms, tornadoes and hail are notorious visitors to Denver and across eastern Colorado during the month.