Climatological Report (Monthly)
Issued by NWS Denver/Boulder, CO

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CXUS55 KBOU 111109 CCA
CLMDEN

CLIMATE REPORT
NATIONAL WEATHER SERVICE DENVER/BOULDER CO
244 AM MDT SUN OCT 1 2017

...................................

...THE DENVER CO CLIMATE SUMMARY FOR THE MONTH OF SEPTEMBER 2017...

CLIMATE NORMAL PERIOD 1981 TO 2010
CLIMATE RECORD PERIOD 1872 TO 2017

WEATHER         OBSERVED          NORMAL  DEPART  LAST YEAR`S
                 VALUE   DATE(S)  VALUE   FROM    VALUE  DATE(S)
                                          NORMAL
................................................................
TEMPERATURE (F)
RECORD
 HIGH              97   09/03/2017
                        09/06/2013
                        09/05/2013
 LOW               17   09/29/1985
HIGHEST            97R  09/03        91       6       93  09/05
LOWEST             40   09/20        35       5       37  09/10
AVG. MAXIMUM     79.0              78.5     0.5     82.3
AVG. MINIMUM     51.3              48.3     3.0     49.7
MEAN             65.1              63.4     1.7     66.0
DAYS MAX >= 90      9               3.4     5.6        6
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           1.26              0.96    0.30     0.28
DAILY AVG.       0.04              0.03    0.01     0.01
DAYS >= .01         6               6.5    -0.5        4
DAYS >= .10         2               3.3    -1.3        1
DAYS >= .50         1               0.6     0.4        0
DAYS >= 1.00        0               0.1    -0.1        0
GREATEST
 24 HR. TOTAL    0.83   09/23 TO 09/23           09/12 TO 09/12

SNOWFALL (INCHES)
RECORDS
 TOTAL             0.0
TOTALS            0.0               1.3

DEGREE_DAYS
HEATING TOTAL     122               125      -3       64
 SINCE 7/1        130               141     -11       79
COOLING TOTAL     131                76      55       99
 SINCE 1/1        880               764     116      861

FREEZE DATES
RECORD
 EARLIEST     09/08/1962
 LATEST       06/08/2007
EARLIEST                        10/07
LATEST                          05/05
...................................................

WIND (MPH)
AVERAGE WIND SPEED              9.6
RESULTANT WIND SPEED/DIRECTION   2/165
HIGHEST WIND SPEED/DIRECTION    40/020    DATE  09/19
HIGHEST GUST SPEED/DIRECTION    48/030    DATE  09/19

SKY COVER
POSSIBLE SUNSHINE (PERCENT)   MM
AVERAGE SKY COVER           0.50
NUMBER OF DAYS FAIR            9
NUMBER OF DAYS PC             15
NUMBER OF DAYS CLOUDY          6

AVERAGE RH (PERCENT)     48

WEATHER CONDITIONS. NUMBER OF DAYS WITH
THUNDERSTORM              2     MIXED PRECIP               0
HEAVY RAIN                1     RAIN                       1
LIGHT RAIN               10     FREEZING RAIN              0
LT FREEZING RAIN          0     HAIL                       0
HEAVY SNOW                0     SNOW                       0
LIGHT SNOW                0     SLEET                      0
FOG                       8     FOG W/VIS <= 1/4 MILE      1
HAZE                     10

-  INDICATES NEGATIVE NUMBERS.
R  INDICATES RECORD WAS SET OR TIED.
MM INDICATES DATA IS MISSING.
T  INDICATES TRACE AMOUNT.

...SEPTEMBER 2017...WARMER AND SLIGHTLY WETTER THAN NORMAL...

SEPTEMBER WAS A TAIL OF TWO MONTHS AS THE FIRST TWO-THIRDS OF THE
MONTH WERE TOP FIVE WARMEST BUT THE LAST 8 DAYS WERE MUCH COOLER. A
PERSISTENT UPPER LEVEL RIDGE OF HIGH PRESSURE OVER THE ROCKY
MOUNTAIN REGION DOMINATED THE MAJORITY OF THE WEATHER FOR THE FIRST
THREE WEEKS OF THE MONTH. THIS RIDGE WAS PARTICULARLY STRONG ON THE
3RD WHEN DENVER REACHED A HIGH TEMPERATURE OF 97 DEGREES TYING THE
WARMEST TEMPERATURE ON RECORD FOR THE MONTH OF SEPTEMBER. A BRIEF
BREAK IN THE HEAT OCCURRED ON THE 5TH AND 6TH BEFORE ANOTHER STRETCH
OF HEAT BEGAN. DENVER SAW FIVE 90 DEGREE OR ABOVE HIGH TEMPERATURES
IN SIX DAYS FROM THE 9TH TO THE 14TH. THE FINAL 90 DEGREE OR ABOVE
HIGH OCCURRED ON THE 21ST WITH A RECORD HIGH OF 92. THIS LEAD DENVER
TO TIE THE RECORD FOR MOST 90 DEGREE HIGH TEMPERATURES FOR THE MONTH
OF SEPTEMBER WHICH IS 9. TO GO ALONG WITH THE HEAT, THE FIRST 22
DAYS OF THE MONTH WERE ABNORMALLY DRY ACROSS NORTHERN COLORADO.
LIMON ONLY RECEIVED 0.01 INCHES OF RAIN WHILE DENVER RECEIVED 0.02
INCHES AND CENTENNIAL AIRPORT RECEIVED 0.03 INCHES DURING THIS
PERIOD. A MAJOR PATTERN CHANGE THEN BEGAN ON THE 23RD AS A STRONG
UPPER LEVEL TROUGH OF LOW PRESSURE MOVED OVER THE ROCKY MOUNTAIN
REGION. THIS SYSTEM BROUGHT THE SEASON`S FIRST ACCUMULATING SNOW TO
MANY ELEVATIONS ABOVE 10,000 FEET. IN ADDITION, IT BROUGHT SOAKING
RAINS TO THE FOOTHILLS AND PLAINS AS DENVER RECEIVED 0.83 INCHES OF
RAIN, THE HIGHEST SINGLE DAY TOTAL FOR THE MONTH. AS THE TROUGH
LINGERED OVER THE FOUR CORNERS REGION, PRECIPITATION CONTINUED TO
FALL ACROSS COLORADO IN WAVES FOR THE REST OF THE MONTH. THIS
PATTERN SHIFT THE LAST 8 DAYS OF SEPTEMBER ALLOWED FOR DENVER TO
FINISH THE MONTH 0.30 INCHES OF RAIN ABOVE NORMAL, WHILE
TEMPERATURES FINISHED 1.7 DEGREES ABOVE AVERAGE.

TEMPERATURES:

THE AVERAGE TEMPERATURE AT DENVER INTERNATIONAL AIRPORT FOR THE
MONTH WAS 65.1 DEGREES F, WHICH IS 1.7 DEGREES ABOVE NORMAL. THE
WARMEST SEPTEMBER ON RECORD OCCURRED IN 2015 WITH AN AVERAGE MONTHLY
TEMPERATURE OF 69.4 DEGREES F. THE COLDEST SEPTEMBER ON RECORD WAS
54.7 DEGREES BACK IN 1912. ON THE 3RD, THE TEMPERATURE CLIMBED TO 97
DEGREES F WHICH IS THE HIGHEST TEMPERATURE RECORDED DURING THE
MONTH. THE COLDEST TEMPERATURE OF 40 DEGREES F OCCURRED ON THE
MORNING OF THE 20TH.

TEN WARMEST SEPTEMBER`S IN DENVER WEATHER HISTORY SINCE 1872:

69.4 2015
68.3 1948
68.2 1981...1931
68.0 1998
67.7 1933
67.6 1947
67.2 2005...1994
67.0 2010...1939

TEN COLDEST SEPTEMBER`S IN DENVER WEATHER HISTORY SINCE 1872:

54.7 1912
55.6 1965
56.3 1961
57.5 1971
58.1 1918
58.8 1985
58.9 2006...1929
59.2 1999
59.3 2003...1913

PRECIPITATION:

PRECIPITATION FOR THE MONTH OF SEPTEMBER AT DENVER INTERNATIONAL
AIRPORT WAS 1.26 INCHES, WHICH IS 0.30 INCHES ABOVE THE NORMAL OF
0.96 INCHES. THERE WERE 6 DAYS WITH MEASURABLE PRECIPITATION DURING
THE MONTH. 0.83 INCHES OF PRECIPITATION FELL ON THE 23RD, WHICH IS
THE GREATEST DAILY AMOUNT FOR THE MONTH.

TEN WETTEST SEPTEMBER`S IN DENVER WEATHER HISTORY SINCE 1872:

5.61 INCHES 2013
4.67 INCHES 1961
3.78 INCHES 1909
3.70 INCHES 1902
3.42 INCHES 1938
2.95 INCHES 2012
2.89 INCHES 1936...1918...1875
2.85 INCHES 1973...1971

TEN DRIEST SEPTEMBER`S IN DENVER WEATHER HISTORY SINCE 1872:

TRACE 1944...1892
0.01 INCHES 1992...1956
0.02 INCHES 1921...1879
0.05 INCHES 1983
0.06 INCHES 2010...1920...1882

THERE WERE 2 DAYS IN WHICH THUNDER WAS OBSERVED AT DENVER
INTERNATIONAL AIRPORT AND 1 DAY WITH DENSE FOG WITH A VISIBILITY AT
OR BELOW 1/4 MILE DURING THE MONTH. THE PEAK WIND GUST OF 48 MPH
FROM THE NORTHEAST OCCURRED ON THE 19TH.

$$



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