A Statistical Preview of Denver's October Weather

   ...A STATISTICAL PREVIEW OF DENVER'S OCTOBER WEATHER...
 
ACCORDING TO THE CALENDAR, AS SUMMER FLIPPED OVER TO FALL IN LATE SEPTEMBER, THE THERMOMETERS ACROSS THE REGION REGISTERED NO SIGNIFICANT CHANGE TO THE COOL SIDE. SEPTEMBER 2012 REMAINED CONSISTENT WITH THE PREVIOUS FEW MONTHS OF ABOVE NORMAL TEMPERATURES AS A DRY AND STABLE RIDGE OF HIGH PRESSURE DOMINATED THE WESTERN, CENTRAL AND SOUTHERN UNITED STATES.
 
AFTER THE RECORD HOT MONTHS OF JUNE AND JULY, AUGUST 2012 FINISHED THE MONTH AS THE 5TH WARMEST AND 4TH DRIEST IN DENVER'S 141 YEAR HISTORY. OVER THE FINAL FEW DAYS OF THE SEPTEMBER 2012, THE MONTH SLIPPED OUT OF A POSSIBLE TOP 10 WARMEST RANKING AS A COOL TROUGH OF LOW PRESSURE PASSED OVER THE STATE. THIS STORM SYSTEM BROUGHT COOLER TEMPERATURES AND MUCH NEEDED RAIN TO THE CENTRAL ROCKIES. IN FACT, ON THE EVENING OF THE 26TH, ENOUGH RAIN FELL AT DENVER INTERNATIONAL AIRPORT TO LAUNCH THE MONTHLY PRECIPITATION TOTAL TO A 5TH WETTEST SEPTEMBER RANKING. PRECIPITATION RECORDS IN DENVER BEGAN IN 1872.
 
CLIMATOLOGICALLY, AFTER FAIRLY STABLE TEMPERATURE VARIATION DURING THE WARMEST MONTHS OF JULY AND AUGUST, TEMPERATURE SPREADS ACROSS THE MONTH OF SEPTEMBER BEGIN TO WIDEN AS DRYER AND COOLER AIR FROM THE NORTHERN PLAINS AND CANADIAN REGION PERIODICALLY WORK THEIR WAY INTO THE HIGH PLAINS OF EASTERN COLORADO BEHIND PASSING STORM SYSTEMS TO THE NORTH. DURING THE MONTH OF OCTOBER IN DENVER, TEMPERATURE SPREADS CAN WIDEN EVEN FURTHER AS THE REGION TRULY MOVES OUT OF THE WARM MONTHS FOR GOOD.
 
DENVER'S MONTHLY MEAN TEMPERATURE FOR OCTOBER IS 50.9 DEGREES (1981-2010 AVERAGES) AND IS DENVER'S FIFTH WARMEST MONTH OF THE YEAR BEHIND JULY, AUGUST, JUNE AND MAY RESPECTIVELY. THE MONTH STARTS WITH A NORMAL HIGH OF 72 DEGREES AND ENDS WITH A NORMAL HIGH OF 59 DEGREES. FOR LOW TEMPERATURES, THE MONTH BEGINS WITH A NORMAL OF 42 DEGREES AND TRENDS BELOW THE FREEZING MARK TO FINISH WITH A NORMAL OF 31.
 
THE WARMEST TEMPERATURE EVER RECORDED DURING THE MONTH OF OCTOBER, SINCE RECORDS BEGAN IN 1872, WAS 90 DEGREES AND OCCURRED ON THE FIRST DAY ON THE MONTH WAY BACK IN 1892. THIS IS ALSO THE LATEST 90 DEGREE OR HIGHER TEMPERATURE DENVER HAS RECORDED. THE COLDEST TEMPERATURE EVER RECORDED IN DENVER FOR OCTOBER WAS A FRIGID -2 DEGREES AND OCCURRED ON THE 29TH DAY OF 1917.
 
OCTOBER: DENVER'S TOP 5 WARMEST (MEAN TEMPERATURES):
 
59.9 DEGREES 1950
57.9         1963
57.8         1934
57.4         1933
57.0         1947
 
OCTOBER: DENVER'S TOP 5 COLDEST (MEAN TEMPERATURES):
 
39.0 DEGREES 1969
42.9         2009
43.3         1925
43.9         2002
44.3         1923
 
OCTOBER: DENVER'S WETTEST
 
4.17 INCHES 1969
3.92        1892
3.72        1942
3.50        1923
3.47        1984
 
OCTOBER: DENVER'S DRIEST
 
   T INCHES 1934
0.01        1933
0.05        1944, 1962
0.06        1948, 1954, 1988
0.08        2001, 2003
 
ALTHOUGH SEPTEMBER IS THE FIRST MONTH OF THE SNOW SEASON IN DENVER, OCTOBER IS THE MONTH WHEN DENVER AND THE ENTIRE FRONT RANGE BEGIN TO SEE THE STRONG LIKELIHOOD OF COLD PACIFIC STORM SYSTEMS BRINGING THE SEASON'S FIRST REAL SNOWFALL. SINCE SNOW MEASURING BEGAN IN DENVER IN 1882, MONTHLY SNOW TOTALS OF GREATER THAN 0.1" HAS OCCURRED 100 TIMES WITH 15 YEARS RECEIVING A TRACE AND THE 15 YEARS MISSING OUT ENTIRELY FROM ANY SNOW.
 
OCTOBER: DENVER`S SNOWIEST
 
31.2 INCHES 1969
22.7        1906
22.1        1997
17.8        1923
17.2        2009
 
OCTOBER: DENVER'S LEAST SNOWIEST
 
 0.0 15 OCCURRENCES
   T 15 OCCURRENCES
 
     ...THE OUTLOOK FOR OCTOBER 2012...
 
AFTER 7 CONSECUTIVE MONTHS OF ABOVE NORMAL TEMPERATURES IN THE DENVER AREA ALONG WITH BELOW NORMAL PRECIPITATION TOTALS FOR SPRING AND SUMMER PERIOD, THE MID TO LONG RANGE FORECAST MODELS CONTINUE TO INDICATE A BIAS TOWARD THE STABLE DRY WEST TO SOUTHWESTERLY FLOW ALOFT OVER COLORADO. THE CLIMATE PREDICTION CENTER'S LONG RANGE OUTLOOK INDICATES A BIAS TOWARD ABOVE NORMAL TEMPERATURES WITH PRECIPITATION PROBABILITIES HOLDING NEAR SEASONAL NORMALS REGION WIDE.
 
     ...OCTOBER STATISTICS...
 
...TEMPERATURES (1981-2010 NORMALS)...
 
AVERAGE HIGH........................... 65.3
AVERAGE LOW............................ 36.6
MONTHLY MEAN........................... 50.9
DAYS WITH HIGH 90 OR ABOVE.............   0 (<0.1)
DAYS WITH HIGH 32 OR BELOW.............   0 (0.4)
DAYS WITH LOW 32 OR BELOW..............   9 (8.5)
DAYS WITH LOWS ZERO OR BELOW...........   0 (<0.1)
 
...PRECIPITATION...
 
MONTHLY MEAN...........................   1.02 INCHES
DAYS WITH MEASURABLE PRECIPITATION.....   5 (5.3)
AVERAGE SNOWFALL.......................   4.0 INCHES
 
...MISCELLANEOUS OCTOBER AVERAGES...
 
HEATING DEGREE DAYS.................... 440
COOLING DEGREE DAYS....................   5
WIND SPEED (MPH).......................   7.8*
WIND DIRECTION......................... SOUTH*
DAYS WITH THUNDERSTORMS................   1* (0.8)
DAYS WITH DENSE FOG....................   1* (0.6)
PERCENT OF SUNSHINE.................... 72*
(NOTE: SUNSHINE DATA ARE NO LONGER COLLECTED AS OF OCTOBER 1, 2009)
 
* = 1971-2002 NORMALS
 
...OCTOBER EXTREMES...
 
RECORD HIGH............................ 90 DEGREES ON 10/1/1892
RECORD LOW............................. -2 DEGREES ON 10/29/1917
WARMEST................................ 59.9 DEGREES IN 1950
MAXIMUM COOLING DEGREE DAYS............ 14 IN 2006, 2005
MINIMUM COOLING DEGREE DAYS............   0 NUMEROUS (22) YEARS
COLDEST................................ 39.0 DEGREES IN 1969
MAXIMUM HEATING DEGREE DAYS............ 801 IN 1969
MINIMUM HEATING DEGREE DAYS............ 159 IN 1950
WETTEST................................   4.17 INCHES IN 1969
DRIEST................................. TRACE IN 1934
SNOWIEST............................... 31.2 INCHES 1969
LEAST SNOWY............................   0.0 INCHES NUMEROUS YEARS
                                                     (15)
 
FREDIN


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