With the mercury stuck stubbornly at the top of the scale and barely a few raindrops falling into the bucket, September 2015 will be going into the books as one of the warmest and driest on record.
High pressure dominated the entire region during the month. This allowed temperatures to consistently climb above normal and helped prevent moisture from arriving in any significant amounts. At Denver International Airport, 27 of the 30 days had above normal temperatures. Thornton’s overall temperatures were cooler than DIA’s but we were still quite a bit warmer than average.
The monthly average temperature in Thornton came in at 67.1 degrees. Out at the airport where the Mile High City’s official measurements are taken, the average was 69.4 degrees.
Denver’s historical average for September is 63.4 so both locations came in well above normal. Officially, September 2015 ranks as the warmest September on record, easily jumping to the number one spot over September 1948 which had an average of 68.3 degrees.
Undoubtedly the big difference between measurements at DIA and other locations in the metro area are yet another example of the airport’s readings consistently being an outlier from the reality seen in more populated areas. This has been an ongoing problem since the National Weather Service moved the official station from Stapleton.
The warmest mercury reading in Thornton during the month was 94 degrees on the 13th. The coldest came on the 19th when temperatures dipped to 40 degrees in the early morning hours. Eight days in Thornton topped out above the 90 degree mark.
At the airport, Denver’s warmest reading of 92 degrees came on September 2. It’s coldest on September 19 (44 degrees). The airport saw seven days with above 90 degree maximums.
Just as the month was exceedingly warm, it also was very dry. Thornton saw a mere 0.09 inches fall in its rain bucket and Denver recorded 0.11 inches. Both were far short of the September precipitation average of 0.96 inches.
DIA’s measurement means September 2015 goes into the books with the 9th least amount of precipitation in September since 1872 (16th driest overall).
Click here to view Thornton’s September 2015 climate report.
From the National Weather Service:
CLIMATE REPORT
NATIONAL WEATHER SERVICE BOULDER, CO
244 AM MDT THU OCT 1 2015
...THE DENVER CO CLIMATE SUMMARY FOR THE MONTH OF SEPTEMBER 2015...
CLIMATE NORMAL PERIOD 1981 TO 2010
CLIMATE RECORD PERIOD 1872 TO 2015
WEATHER OBSERVED NORMAL DEPART LAST YEAR`S
VALUE DATE(S) VALUE FROM VALUE DATE(S)
NORMAL
................................................................
TEMPERATURE (F)
RECORD
HIGH 97 09/06/2013
09/05/2013
09/04/1995
LOW 17 09/29/1985
HIGHEST 92 09/02 91 1 94 09/03
LOWEST 44 09/19 35 9 33 09/12
AVG. MAXIMUM 85.2 78.5 6.7 78.9
AVG. MINIMUM 53.5 48.3 5.2 50.6
MEAN 69.4 63.4 6.0 64.8
DAYS MAX >= 90 7 3.4 3.6 2
DAYS MAX <= 32 0 0.0 0.0 0
DAYS MIN <= 32 0 0.8 -0.8 0
DAYS MIN <= 0 0 0.0 0.0 0
PRECIPITATION (INCHES)
RECORD
MAXIMUM 5.61 2013
MINIMUM T 1892 1944
TOTALS 0.11 0.96 -0.85 1.79
DAILY AVG. 0.00 0.03 -0.03 0.06
DAYS >= .01 3 6.5 -3.5 9
DAYS >= .10 0 3.3 -3.3 4
DAYS >= .50 0 0.6 -0.6 1
DAYS >= 1.00 0 0.1 -0.1 1
GREATEST
24 HR. TOTAL 0.12 08/31 TO 09/01 09/29 TO 09/29
09/28 TO 09/29
09/29 TO 09/29
STORM TOTAL MM MM
(MM/DD(HH)) MM 09/29(00) TO 09/29(00)
09/29(00) TO 09/29(00)9
09/29(00) TO 09/29(00)9
SNOWFALL (INCHES)
RECORDS
TOTAL MM MM
TOTALS 0.0 1.3
DEGREE_DAYS
HEATING TOTAL 9 125 -116 91
SINCE 7/1 27 141 -114 98
COOLING TOTAL 148 76 72 88
SINCE 1/1 861 764 97 701
FREEZE DATES
RECORD
EARLIEST 09/08/1962
LATEST 06/08/2007
EARLIEST 10/07
LATEST 05/05
..........................................................
WIND (MPH)
AVERAGE WIND SPEED 9.0
RESULTANT WIND SPEED/DIRECTION 2/195
HIGHEST WIND SPEED/DIRECTION 35/280 DATE 09/07
HIGHEST GUST SPEED/DIRECTION 54/270 DATE 09/07
SKY COVER
POSSIBLE SUNSHINE (PERCENT) MM
AVERAGE SKY COVER 0.40
NUMBER OF DAYS FAIR 12
NUMBER OF DAYS PC 17
NUMBER OF DAYS CLOUDY 1
AVERAGE RH (PERCENT) 41
WEATHER CONDITIONS. NUMBER OF DAYS WITH
THUNDERSTORM 6 MIXED PRECIP 0
HEAVY RAIN 0 RAIN 3
LIGHT RAIN 7 FREEZING RAIN 0
LT FREEZING RAIN 0 HAIL 3
HEAVY SNOW 0 SNOW 0
LIGHT SNOW 0 SLEET 0
FOG 3 FOG W/VIS <= 1/4 MILE 5
HAZE 1
- INDICATES NEGATIVE NUMBERS.
R INDICATES RECORD WAS SET OR TIED.
MM INDICATES DATA IS MISSING.
T INDICATES TRACE AMOUNT.