Autumn 2011 Climate Summary

During Meteorological Autumn (September 1 through November 30), both La Crosse Municipal and Rochester International airports were warmer and drier than normal.  In addition, autumn snowfall was below normal for both locations.  This is what we typically experience during a La Niña autumn.

The information below provides more details on these statistics.

La Crosse, WI:

Temperatures...

From September 1 through November 30, 2011, La Crosse Municipal Airport had an average temperature of 51.3 degrees.  This was 1.7 degrees above the 1981-2010 normal of 49.6 degrees.  The average high temperature was 61.2 degrees which was 1.3 degrees warmer than 1981-2010 normal of 59.0 degrees.  The average low temperature was 41.4 degrees which was 1.1 degrees warmer than 1981-2010 normal of 40.3 degrees.  The table below contains the monthly average temperatures and their departures from normal for the autumn of 2011.

           Autumn 2011 Temperatures
               in La Crosse WI

                  Average            Departure
   Month        Temperature         from Normal
   -----        -----------         -----------
   September   60.5 degrees        -2.3 degrees
   October     53.7 degrees        +3.5 degrees 
   November    39.8 degrees        +3.9 degrees 
 
   Autumn      51.3 degrees        +1.7 degrees


This autumn's temperatures were very typical for a La Niña.  September temperatures averaged below normal (-2.3 degrees).  This has occurred during twelve of the twenty (60.0 percent) La Niñas since 1950.  Meanwhile temperatures averaged above normal during both October (+3.5 degrees) and November (+3.9 degrees).  During these two months...the average temperature has been warmer than normal during seventeen of the twenty (85.0 percent) La Niñas since 1950.

One of the warmest stretches of weather during the autumn occurred from October 2nd through October 12th.  During this 11 day stretch...the high temperatures were 70 degrees or higher.  This was the second longest stretch of 70-degree days during an October.  The only one which was longer was 16 day stretch back in 1879 (October 1st through October 16th).

Precipitation...

From September 1 through November 30, 2011, La Crosse Municipal Airport received 5.58 inches of precipitation.  This was 3.38 inches above the 1971-2000 normal of 7.74 inches.  The table below contains the monthly precipitation totals and their departures from normal for the autumn of 2011.

          Autumn 2011 Precipitation
               in La Crosse WI

                Precipitation         Departure
   Month            Total            from Normal
   -----        ------------         -----------
   September    3.04 inches         -0.52 inches 
   October      1.63 inches         -0.54 inches  
   November     0.91 inches         -1.10 inches 
 
   Autumn       5.58 inches         -2.16 inches


Dry autumns are fairly common during La Niña.  Since 1950, 14 out of 20 (70 percent) La Nina autumns had below normal precipitation.  During the autumns, the average precipitation was 6.67 inches which is 0.69 inches below the long-term average of 7.36 inches.

Snowfall...

From September 1 through November 30, 2011, La Crosse Municipal Airport received 0.7 inches of snow.  This was 3.6 inches below the normal of 4.3 inches.  The table below contains the monthly snowfall totals and their departures from normal for the autumn of 2011.

            Autumn 2011 Snowfall
               in La Crosse WI

                  Snowfall            Departure
   Month            Total            from Normal
   -----        ------------         -----------
   September     0.0 inches           0.0 inches
   October       0.0 inches          -0.2 inches  
   November      0.7 inches          -4.1 inches  
 
   Autumn        0.7 inches          -3.6 inches  


The below-normal autumn snowfall is very typical of a La Niña.  Fourteen out of the twenty /70.0 percent/ La Ninas since 1950 have produced below normal autumn snowfall.

Rochester, MN:

Temperatures...6th Warmest

From September 1 through November 30, 2011, Rochester International Airport had an average temperature of 50.3 degrees.  This was 2.6 degrees above the normal of 47.7 degrees.  This was the sixth warmest autumn in Rochester MN.  The table below contains the ten warmest autumns.

               Warmest Autumns
               in Rochester MN
                  1886-2009

                  Average
    Rank        Temperature         Year
    ----        -----------         ----
      1         52.7 degrees        1963
      2         50.7 degrees        2007
                50.7 degrees        2005
      4         50.6 degrees        1953
      5         50.4 degrees        1914
      6         50.3 degrees        2011
      7         50.1 degrees        1998
      8         50.0 degrees        2001
                50.0 degrees        1994
                50.0 degrees        1971


The average high temperature during autumn of 2011 was 60.3 degrees which was 3.2 degrees warmer than 1981-2010 normal of 57.1 degrees.  The average low temperature was 40.2 degrees which was 1.9 degrees warmer than 1981-2010 normal of 38.3 degrees.  The table below contains the monthly average temperatures and their departures from normal for the autumn of 2011.

           Autumn 2011 Temperatures
               in Rochester MN

                  Average            Departure
   Month        Temperature         from Normal
   -----        -----------         -----------
   September   59.3 degrees        -1.6 degrees
   October     53.0 degrees        +4.6 degrees - 10th Warmest
   November    38.5 degrees        +4.7 degrees -  7th Warmest
 
   Autumn      50.3 degrees        +2.6 degrees -  6th Warmest


This autumn's temperatures were very typical for a La Niña.  September temperatures averaged below normal (-1.6 degrees).  This has occurred during eleven of the twenty (55.0 percent) La Niñas since 1950.  Meanwhile temperatures averaged above normal during both October (+4.6 degrees) and November (+4.7 degrees).  During these two months...the average temperature has been warmer than normal during sixteen of the twenty (80.0 percent) La Niñas since 1950.

One of the warmest stretches of weather during the autumn occurred from October 2nd through October 11th.  During this ten day stretch, the high temperatures were 70 degrees or higher.  This tied a similar stretch in 1953 (October 13-22) for the longest stretch of 70 degree days during an October.

Precipitation...10th Driest

From September 1 through November 30, 2011, Rochester International Airport received 3.14 inches of precipitation.  This was 4.46 inches below the 1981-2010 normal 7.60 inches.  This was the tenth driest autumn.  It was the driest autumn since 1999 when 2.08 inches of precipitation fell.  The driest autumn occurred during 1976 when just 1.46 inches of precipitation fell.  The table below contains the ten driest autumns in Rochester MN.

                Driest Autumns
               in Rochester MN
                  1886-2011

                Precipitation
    Rank            Total          Year
    ----        ------------        ----
      1          1.49 inches        1976
      2          2.08 inches        1999
      3          2.34 inches        1944
      4          2.48 inches        1953
      5          2.71 inches        1939
      6          2.76 inches        1910
      7          2.87 inches        1952
      8          3.00 inches        1908
      9          3.09 inches        2003
     10          3.14 inches        2011


The table below contains the monthly precipitation totals and their departures from normal for the autumn of 2011.

          Autumn 2011 Precipitation
               in Rochester MN

                Precipitation         Departure
   Month            Total            from Normal
   -----        ------------         -----------
   September    2.47 inches         -0.98 inches 
   October      0.29 inches         -1.95 inches -  5th driest
   November     0.38 inches         -1.53 inches - 16th driest
 
   Autumn       3.14 inches         -4.46 inches - 10th driest



This dryness resulted in the southeast Minnesota deteriorating from no drought at the beginning of September to a moderate /D1/ to severe (D2) drought by early October.  These conditions then remained fairly constant through the remainder of the autumn. 

Snowfall...

From September 1 through November 30, 2011, Rochester International Airport received just 0.2 inches of snow.  This was 6.7 inches below the 1981-2010 normal of 6.9 inches.  The below-normal autumn snowfall is very typical of a La Niña.  Fourteen out of the twenty (70.0 percent) La Niñas since 1950 have produced below normal autumn snowfall.

The table below contains the monthly snowfall totals and their departures from normal for the autumn of 2011.

            Autumn 2011 Snowfall
               in Rochester MN

                  Snowfall            Departure
   Month            Total            from Normal
   -----        ------------         -----------
   September     0.0 inches           0.0 inches
   October         Trace             -0.8 inches 
   November      0.2 inches          -6.1 inches - 8th Least
 
   Autumn        0.2 inches          -6.9 inches



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