A Statistical Preview of Denver's August Weather

...A STATISTICAL PREVIEW OF DENVER'S AUGUST WEATHER...

LIKE MOST LOCATIONS IN THE UNITED STATES, JULY IS DENVER'S CLIMATOLOGICAL WARMEST MONTH OF THE YEAR AS THE DAILY AVERAGE TEMPERATURES PEAK APPROXIMATELY 4 WEEKS AFTER THE SUMMER SOLSTICE. AS WE MOVE INTO THE MONTH OF AUGUST, THE DOWNWARD SLOPE OF DAILY TEMPERATURE BEGINS FOR ALL OF NORTHERN COLORADO AND CONTINUES DOWNWARD THROUGH LATE JANUARY.

AS THE NORTH AMERICAN MONSOON REMAINS IN FULL FORCE DURING THE EARLY PORTION OF AUGUST, THE DOMINANT RIDGE OF HIGH PRESSURE SUPPLYING THE SUBTROPICAL MOISTURE TYPICALLY BEGINS TO WEAKEN. THIS WEAKENING HINDERS THE ABILITY OF THE DOMINANT RIDGE TO HOLD CONSISTENTLY OVER THE SOUTHERN UNITED STATES LONG ENOUGH TO KEEP THE DEEP SUBTROPICAL MOISTURE SUPPLIED TO THE CENTRAL ROCKIES.

ALTHOUGH THE LOW-LEVEL JET OVER THE CENTRAL UNITED STATES IS STILL PRESENT DURING AUGUST, IT ALSO WEAKENS DURING THE SECOND HALF OF THE MONTH. SIMILAR TO JUNE AND JULY, GULF MOISTURE CAN STILL PUSH IT'S WAY INTO EASTERN COLORADO ON THE WESTERN EDGE OF THE BROAD SPAN OF SOUTHERLY WINDS.

WITH DENVER'S DAILY NORMAL TEMPERATURES PEAKING AND HOLDING STEADY IN LATE JULY, TEMPERATURE VARIATION FOR AUGUST ALSO REMAINS FAIRLY LOW THROUGHOUT THE MONTH. DENVER'S MONTHLY MEAN TEMPERATURE FOR AUGUST IS 72.5 DEGREES (1981-2010 AVERAGES) AND IS DENVER'S SECOND WARMEST MONTH OF THE YEAR BEHIND JULY. AUGUST STARTS THE MONTH WITH A NORMAL HIGH OF 90 DEGREES AND ENDS WITH A NORMAL HIGH OF 84 DEGREES. FOR LOW TEMPERATURES, THE MONTH BEGINS WITH A NORMAL OF 60 DEGREES AND FINISHES WITH A NORMAL OF 54.

THE WARMEST TEMPERATURE EVER RECORDED DURING THE MONTH OF AUGUST, SINCE RECORDS BEGAN IN 1872, WAS 105 DEGREES ON THE 8TH DAY OF 1878. THE COLDEST TEMPERATURE EVER RECORDED IN DENVER FOR AUGUST WAS 40 DEGREES AND OCCURRED 4 TIMES. THE FIRST OCCURRENCE WAS ON THE 22ND DAY OF 1904 WITH THE OTHERS OCCURRING IN A 3 DAY COOL PERIOD ON THE 24TH, 25TH AND 26TH OF 1910.

AUGUST: DENVER'S TOP 10 WARMEST (MEAN TEMPERATURES):

77.0 DEGREES 2011

76.8         1937

75.4         2007

75.3         1995

75.0         2012

75.0         1994

74.7         1938

74.6         2013

74.6         1878

74.5         2000

AUGUST: DENVER'S TOP 10 COLDEST (MEAN TEMPERATURES):

66.5 DEGREES 1915

66.6         1927

67.7         1920

67.8         1884

68.0         1888

68.1         1968

68.2         2004

68.2         1967

68.4         1992

68.4         1917

ALONG WITH JUNE AND JULY, THE POSSIBILITY OF SEVERE WEATHER STILL EXISTS FOR THE MONTH OF AUGUST, HOWEVER THE CHANCES DIMINISH TOWARD THE LATTER HALF. RAINFALL TOTALS FROM STRONG, RAIN DUMPING THUNDERSTORMS IS STILL THE MEASURE OF INTEREST FOR AUGUST AS WEAK AIRMASS COLLISIONS AND WARM TEMPERATURES ALOFT OFTEN INHIBIT THE LARGEST HAIL DEVELOPMENT. DENVER'S THE 8TH WETTEST MONTH IN DENVER HISTORY OCCURRED IN AUGUST, 1979 AS STAPLETON INTERNATIONAL AIRPORT RECEIVED 5.85 INCHES. THE 7TH HIGHEST 24 HOUR PRECIPITATION TOTAL IN DENVER HISTORY OCCURRED ON AUGUST 23RD, 1921 AS 2.93 INCHES OF RAIN FELL.

AUGUST: DENVER'S WETTEST

5.85 INCHES 1979

4.47        1951

4.03        2008

3.87        1923

3.69        1991

3.52        1997

3.49        1921

3.37        1999

3.22        1936

3.20        1984

AUGUST: DENVER'S DRIEST

0.02 INCHES 1924

0.05        1917

0.05        1900

0.06        1960

0.11        2012

0.16        1974

0.19        1948

0.23        1907

0.25        1959

0.26        1978

                   ...THE OUTLOOK FOR AUGUST 2015...

AFTER A SLIGHTLY WARMER END TO THE MONTH OF JULY 2015 WITH NEAR NORMAL PRECIPITATION, THE MID TO LONG RANGE FORECAST MODELS INDICATE A BIAS TOWARD THE STABLE RIDGE OF HIGH PRESSURE HOLDING OVER THE WESTERN UNITED STATES FOR THE FIRST 10 DAYS THE MONTH MOST OF AUGUST. THIS WILL ALLOW FOR SUBTROPICAL MOISTURE TO CONTINUE TO PERIODICALLY DRAW NORTHWARD INTO THE MOUNTAIN STATES WHILE BRINGING BRING A BIAS TOWARD ABOVE NORMAL PRECIPITATION. TEMPERATURES THROUGH AUGUST ARE EXPECTED TO REMAIN NEAR TO SLIGHTL BELOW SEASONAL NORMALS.

                       ...AUGUST STATISTICS...

...TEMPERATURES (1981-2010 NORMALS)...

AVERAGE HIGH...........................  87.2

AVERAGE LOW............................  57.9

MONTHLY MEAN...........................  72.5

DAYS WITH HIGH 90 OR ABOVE.............  12 (11.5)

DAYS WITH HIGH 32 OR BELOW.............   0 (0.0)

DAYS WITH LOW 32 OR BELOW..............   0 (0.0)

DAYS WITH LOWS ZERO OR BELOW...........   0 (0.0)

...PRECIPITATION...

MONTHLY MEAN...........................   1.69 INCHES

DAYS WITH MEASURABLE PRECIPITATION.....   9 (8.6)

AVERAGE SNOWFALL.......................   0.0 INCHES

...MISCELLANEOUS AUGUST AVERAGES...

HEATING DEGREE DAYS....................  10

COOLING DEGREE DAYS.................... 244

WIND SPEED (MPH).......................   8.0*

WIND DIRECTION......................... SOUTH*

DAYS WITH THUNDERSTORMS................   8* (8.3)

DAYS WITH DENSE FOG....................   1* (0.6)

PERCENT OF SUNSHINE....................  71*

(NOTE: SUNSHINE DATA ARE NO LONGER COLLECTED AS OF OCTOBER 1, 2009)

* = 1971-2002 NORMALS

...AUGUST EXTREMES...

RECORD HIGH............................ 105 DEGREES ON 8/8/1878

RECORD LOW.............................  40 DEGREES ON 8/22/1904

                                                       8/24/1910

                                                       8/25/1910

                                                       8/26/1910

WARMEST AUGUST.........................  77.0 DEGREES IN 2011

MAXIMUM COOLING DEGREE DAYS............ 382 IN 2004

MINIMUM COOLING DEGREE DAYS............ 137 IN 2009

COLDEST................................  66.5 DEGREES IN 1915

MAXIMUM HEATING DEGREE DAYS............  38 IN 1920

MINIMUM HEATING DEGREE DAYS............   0 NUMEROUS YEARS

WETTEST................................   5.85 INCHES IN 1979

DRIEST.................................   0.02 IN 1924

WFO BOULDER