2021 Astronomical Spring Climate Summary

Astronomical spring 2021 (March 20-June 19) was unusually warm and dry across the Upper Mississippi River Valley.  Temperatures averaged 2 to 4°F warmer-than-normal across the Upper Mississippi River Valley. Seasonal average temperatures ranged from 50°F at Rushford, MN to 59.2°F at La Crosse Regional Airport.   Normally, spring temperatures average 50°F to 55°F.  It was the 5th warmest spring at La Crosse, WI, and the 10th warmest at Rochester, MN.

Precipitation deficits were up to 7”.  They were the highest (4 to 7”) south of Interstate 90.  Precipitation totals ranged from 3.70” near Oelwein, IA to 12.14” in Grand Marsh, WI. Normally, 9 to 13 inches of precipitation falls during astronomical spring.  It was the 5th driest spring in Rochester, MN.  Due to the spring precipitation deficits along with those over the winter, moderate (D1) to severe (D2) drought conditions developed across the La Crosse Hydrologic Service Area.

Snowfall was below normal across the Upper Mississippi River Valley.  Snow totals ranged from 1” at Sparta, WI to 10.8” near Mantorville, MN.  Normally snowfall ranges from 2.5” to 4” south of Interstate 90 and 4” to 8” north of Interstate 90.  On the morning of May 28, late-season snow fell across northern Buffalo, northern Trempealeau, southern Clark, and northern Jackson counties in west-central and central Wisconsin. Snow amounts ranged from a trace to a few tenths of an inch of snow.  The latest date for snow in the La Crosse County Warning Area is June 2 (1910) in Medford, WI in 1910.  This same system produced snow in northeast Minnesota, northern Wisconsin, and the western half of Upper Michigan. Snow pellets even fell in Chicago on this date. Most places only received a trace of snow.  The only measurable amounts were 0.2” in Marquette, MI, and Chatham, MI.

Temperature Anomalies	Precipitation Anomalies	Snowfall Anomalies

Here are links for more specific details for both La Crosse, WI, and Rochester, MN. 

La Crosse, WI

Astronomical Spring 2021 was Unusually Warmer and Drier-than-Average at La Crosse WI

During the astronomical spring of 2021, temperatures averaged much warmer (4.6 degrees - 5th warmest) and drier (1.86 inches)  than average at La Crosse Regional Airport.  More details on these statistics can be found below.

Temperatures - 5th Warmest

From March 20 through June 19, La Crosse Regional Airport had an average temperature of 59.2 degrees.  This was 4.6 degrees warmer than the long-term average of 54.6 degrees.  This was the 5th warmest spring and the warmest spring since 2012 (59.8 degrees - warmest spring). 8 out of the 16 warmest springs have occurred since 1998 and all ten of the warmest springs have occurred since 1977. The table below lists the ten warmest springs.

 Warmest Astronomical Springs
       in La Crosse WI
          1873-2021
 
           Average
  Rank   Temperature   Year
  ----   -----------   ----
    1   59.8 degrees   2012
    2   59.7 degrees   1977
    3   59.5 degrees   1987
    4   59.4 degrees   1991
    5   59.2 degrees   2021
    6   59.0 degrees   1998
    7   58.8 degrees   2007
    8   58.2 degrees   2010
    9   58.1 degrees   1999
   10   57.9 degrees   1986

• The average high temperature was 70.2 degrees.  This was 5.5 degrees warmer than the long-term average of 64.7 degrees.  This was the 6th warmest average high temperature in a spring.
• The average low temperature was 48.2 degrees.  This was 3.7 degrees warmer than the long-term average of 44.5 degrees. This was the 5th warmest average low temperature in a spring.
   
• The warmest high temperature was 99 degrees on June 5 and June 10. These were the warmest spring temperatures since June 7, 2011.
• The coldest high temperature was 40 degrees on March 31. 
• The warmest low temperature was 75 degrees on June 6.
• The coldest low temperature was 21 degrees on April 1.
   
• There were 13 days in which the high temperature reached or exceeded 90 degrees.
• There were 12 days in which the low temperature was 32 degrees or colder.  

Precipitation 

From March 20 through June 19, La Crosse Regional Airport received 8.36 inches of precipitation.  This was 1.86 inches drier than the long-term average of 10.22 inches.  This was the driest spring since 2005 (6.29 inches - 13th driest). It also ended a 10 year stretch of wetter than average springs.

Measurable precipitation (0.01 inches or greater) fell on 25 days (27.2%) and a trace of precipitation fell on 17 days (18.5%).  

Number of days with...

• None                  51 days (55.4%)
• Trace                  17 days (18.5%)
• 0.01-0.09 inches   8 days ( 8.7%)
• 0.10-0.24 inches   8 days ( 8.7%)
• 0.25-0.49 inches   3 days ( 3.3%)
• 0.50-0.99 inches   3 days ( 3.3%)
• 1.00-1.99 inches   3 days ( 3.3%)  

The wettest spring day was 1.48 inches on June 17. 

Snowfall - Tied for 4th Least

From March 20 through June 19, the snow observer near La Crosse Regional Airport measured a trace of snow.  This was 5 inches below the long-term average of 5.0 inches. This was tied for 4th least with 28 other years.

Measurable snow (0.1 inches or greater) fell on 0 days (0%) and a trace of snow fell on 1 day (1.1%).  

Number of days with...

• No snow       91 Days (98.9%)
• Trace              1 Days  (1.1%)

The snowiest day was a trace of snow on April 14.

Snow Depth 

From March 20 through June 19, the average snow depth near La Crosse Regional Airport was 0 inches.  This was 0.1 inches below the long-term average of 0.1 inches.

The greatest snow depth was 0 inches.

Rochester, MN

Astronomical Spring 2021 was the 10th Warmest and 5th Driest at Rochester MN
 

During the astronomical spring of 2021, temperatures averaged warmer (3.2 degrees - 10th Warmest) and drier than average (4.63 inches - 5th driest spring) at Rochester International Airport.  More details on these statistics can be found below.

Temperatures - 10th Warmest

From March 20 through June 19, Rochester International Airport had an average temperature of 55.4 degrees.  This was 3.2 degrees warmer than the long-term average of 52.2 degrees.  This was the 10th warmest spring and the warmest spring since 2012 (59.8 degrees - warmest spring). 8 out of the 20 warmest springs have occurred since 1998. The table below lists the ten warmest springs.

 Warmest Astronomical Springs
       in Rochester MN
          1886-2021
 
           Average
  Rank   Temperature   Year
  ----   -----------   ----
    1   59.0 degrees   2012
    2   57.9 degrees   1977
    3   57.0 degrees   1987
    4   56.6 degrees   2010
    5   56.4 degrees   2007
    6   56.1 degrees   1991
    7   55.7 degrees   2006
    8   55.6 degrees   1911
    9   55.5 degrees   1941
   10   55.4 degrees   2021

• The average high temperature was 66.2 degrees.  This was 3.4 degrees warmer than the long-term average of 62.8 degrees.  This was the 17th warmest average high temperature in a spring.
• The average low temperature was 44.7 degrees.  This was 3.1 degrees warmer than the long-term average of 41.7 degrees. This was the 11th warmest average low temperature in a spring.  
   
• The warmest high temperature was 95 degrees on June 5 and June 10. 
• The coldest high temperature was 33 degrees on March 31.
• The warmest low temperature was 71 degrees on June 11.
• The coldest low temperature was 16 degrees on April 1.
   
• There were 9 days in which the high temperature reached or exceeded 90 degrees.
• There were 17 days in which the low temperature was 32 degrees or colder.  

Precipitation - 5th Driest

From March 20 through June 19, Rochester International Airport received 5.68 inches of precipitation.  This was 4.63 inches drier than the long-term average of 10.31 inches.  This was the 5th driest spring and the driest spring since 1985 (4.54 inches - 3rd driest spring). The driest spring occurred in 1910 when only 3.17 inches of precipitation fell. The table below lists the ten driest springs.

 Driest Astronomical Springs
       in Rochester MN
          1886-2021
 
        Precipitation
  Rank      Total      Year
  ----  -------------  ----
    1    3.17 inches   1910
    2    4.15 inches   1972
    3    4.54 inches   1985
    4    5.31 inches   1964
    5    5.68 inches   2021
    6    5.97 inches   1932
    7    6.08 inches   1933
    8    6.15 inches   1989
    9    6.19 inches   1963
   10    6.23 inches   1950

This spring ended an 8 year stretch of wetter than average springs.  The average precipitation during those springs was 14.05 inches.

Measurable precipitation (0.01 inches or greater) fell on 24 days (26.1%) and a trace of precipitation fell on 15 days (16.3%).  

Number of days with...

• None                   53 days (57.6%)
• Trace                   24 days (26.1%)
• 0.01-0.09 inches   9 days ( 9.8%)
• 0.10-0.24 inches   7 days ( 7.6%)
• 0.25-0.49 inches   4 days ( 4.3%)
• 0.50-0.99 inches   3 days ( 3.3%)
• 1.00-1.99 inches   1 days ( 1.1%) 

The wettest spring day was 1 inch on May 27. This was the lowest value since 1997 when the wettest day was 0.85 inches.

Snowfall - Tied for the Least

From March 20 through June 19, the snow observer near Rochester International Airport measured just a trace of snow.  This was 6.7 inches below the long-term average of 6.7 inches. This spring was tied with 11 other years for the least amount of snow in a spring.  They included:  1941, 1943, 1946, 1948, 1958, 1998, 1999, 2004, 2010, 2012, and 2017.

Measurable snow (0.1 inches or greater) fell on 0 days (0%) and a trace of precipitation fell on 5 days (5.4%). 

Number of days with...

• No snow       87 Days (94.6%)
• Trace              5 Days  (5.4%)

The snowiest days were a trace of snow on March 27, March 28, April 13, April 14, and April 25.

Snow Depth 

From March 20 through June 19, the average snow depth near Rochester International Airport was 0 inches.  This is 0.3 inches below the long-term average of 0.3 inches.

The greatest snow depth was 0 inches.