2026 Astronomical Summer Climate Summary

Upper Mississippi River Climate Summary for Astronomical Summer 2026: Temperatures - Near to Above Normal Temperatures

During the astronomical summer of 2026 (June 21 through September 21), average temperatures ranged from 65.6°F at Medford Taylor County Airport, WI (AWOS) to 73.4°F near Oelwein, IA (COOP) in the Upper Mississippi River Valley. Temperature anomalies ranged from near normal to 5°F warmer than normal. The hottest temperature was 99°F at Boscobel Airport, WI on July 27. Meanwhile, the coldest temperature was 34°F at Black River Falls, WI (RAWS) on September 14.

Precipitation - Highly Variable

Rainfall was highly variable for astronomical summer. Rain totals ranged from 7.10" near Colby, WI (CoCoRaHS) to 28.69" near Spring Valley, MN (CoCoRaHS). Rainfall anomalies ranged from 8" drier than normal to 16" wetter than normal. The highest one-day precipitation was 8.29" near Houston, MN (CoCoRaHS) from September 18 to September 19.
Severe Weather - Above Average
During astronomical summer (June 21-September 21), a total of 102 convective (severe thunderstorm, tornado, and flash flood) warnings were issued. This was the 10th most. The most was 162 warnings in 1998. The 1986-2026 average was 77.6 warnings. A total of 76 severe thunderstorm warnings were issued. This was tied with 1995 for the 11th most. The most was 128 warnings in 1998. The 1986-2026 average was 61.3 warnings. A total of 12 tornado warnings were issued. This was tied with 2009 and 2025 for the 8th most. The most was 26 warnings in 1997. The 1986-2026 average was 7.2 warnings. A total of 14 flash flood warnings were issued. The most was 46 warnings in 2016. The 1986-2026 average was 10.7 warnings.

Below are the climate summaries for the 2026 astronomical spring in La Crosse, WI, and Rochester, MN

La Crosse, WI

2026 Astronomical Summer was Warmer and Wetter than the Long-Term Average in La Crosse, WI
 

During the astronomical summer of 2026 (June 21 through September 21), it was warmer and wetter than average at La Crosse Regional Airport. Records date back to 1873. More details are listed below... 

• During astronomical summer, La Crosse Regional Airport had an average temperature of 72.7°F.
• This was 2.4°F warmer than the long-term average (1873-2025) of 70.3°F.
• This was tied for the 19th warmest astronomical summer with 2012.
• Below are the 20 warmest astronomical summers in La Crosse, WI.

Warmest Astronomical Summers
    in La Crosse, WI
      1873-2026

Rank  Avg Temp     Year
----  --------     ----
 1     74.5°F      1936
 2     74.4°F      1931
 3     74.2°F      1955
 4     73.9°F      2018
       73.9°F      1998
       73.9°F      1980
 7     73.7°F      1988
 8     73.5°F      1948
 9     73.4°F      2019
       73.4°F      2005
       73.4°F      1995
12     73.3°F      1947
       73.3°F      1937
14     73.1°F      2022
       73.1°F      2021
       73.1°F      2016
       73.1°F      2002
18     72.8°F      1983
19     72.7°F      2026
       72.7°F      2012   

• This was the 17th consecutive summer (dating back to 2010) to average warmer than the long-term average. Since 1995, 28 out of 32 astronomical summers have been warmer than the long-term average. This includes the 4th warmest (73.9°F - 1998 and 2018 are tied), 9th warmest (73.4°F - 1995, 2005, and 2019 are tied), 14th warmest (73.1°F - 2002, 2016, 2021, and 2022 are tied), 19th warmest (72.7°F - 2012 and 2026 are tied), 22nd warmest (72.6°F - 2023), and 24th warmest (72.5°F - 1874, 2013, and 2025).
• The average maximum temperature was 82.2°F. This was 1.6°F warmer than the long-term average of 80.6°F. 
• The average minimum temperature was 63.1°F. This was 3°F warmer than the long-term average of 60.1°F. This was the 8th warmest.

Other temperature tidbits this summer...

• The hottest temperature was 97°F on July 27. 
• The coldest high temperature was 63°F on September 21. 
• The warmest low temperature was 81°F on June 30. This was the warmest June low temperature. The previous record was 80°F on June 29, 1931 and June 22, 2025.
• The coldest low temperature was 46°F on September 14.
• The temperature climbed to or exceeded 90°F on 12 days. Normally, there are 13 days in summer.

Rainfall - 16th Wettest

• During the astronomical summer, La Crosse Regional Airport received 17.32" of rain which was 5.26" wetter than the long-term average (1873-2025) of 12.06".
• This was the 16th wettest summer.
• Below are the 20 wettest summers for La Crosse, WI.

Wettest Astronomical Summers
    in La Crosse, WI
      1873-2026

Rank   Rainfall     Year
----   --------     ----
 1   21.93 inches   2021
 2   21.73 inches   2016
 3   21.57 inches   1938
 4   21.42 inches   1928
 5   20.87 inches   1881
 6   20.20 inches   1980
 7   19.73 inches   2007
 8   19.56 inches   2010
 9   19.11 inches   1981
10   18.28 inches   1884
11   18.10 inches   1990
12   18.06 inches   1978
13   18.00 inches   1942
14   17.99 inches   1906
15   17.48 inches   1994
16   17.32 inches   2026
17   17.18 inches   1875
18   16.99 inches   1987
19   16.91 inches   1934
20   16.87 inches   1885

• 8 out of the last 13 summers have been wetter than the long-term average. This includes the wettest (2021 - 21.93"); 2nd wettest (2016 - 21.73"); 16th wettest (2026 - 17.32"); 22nd wettest (2018 - 16.66"); and 25th wettest (2019 - 16.52").
• The wettest calendar day occurred on July 16 when 2.29" of rain fell. 
• Measurable rain fell on 35 days (37.6%) and trace amounts fell on another 5 days (5.4%). 

Here is a breakdown of the summer rain...

• None             53 days - 53.6%
• Trace             5 days -  5.4%
• 0.01-0.09 inches 14 days - 15.1%
• 0.10-0.24 inches  5 days -  5.4%
• 0.25-0.49 inches  4 days -  4.3%
• 0.50-0.99 inches  8 days -  8.6%
• 1.00-1.99 inches  2 days -  2.2%
• 2.00-2.99 inches  2 day  -  2.2%

Mississippi River at La Crosse - Below Normal

• During astronomical summer, the average 7 am stage for the Mississippi River at La Crosse was 5.15 feet.
• This was 0.71 feet below the 1938-2026 average of 5.86 feet.
• The maximum stage was 6.07 feet on July 3.
• The minimum stage was 4.52 feet on July 22.

Rochester, MN  
 

Astronomical Summer was Warmer and Wetter than the Long-Term Average in Rochester, MN

During the astronomical summer of 2026 (June 21 through September 21), it was warmer (10th warmest) and wetter (11th wettest) than the long-term average (1887-2026) at Rochester International Airport. More details are listed below...

Other temperature tidbits this summer.... ​

• The hottest temperature was 94°F on July 27. 
• The coldest high temperature was 59°F on September 21. 
• The warmest low temperature was 74°F on June 29.
• The coldest temperature was 45°F on September 14. 
• The temperature climbed to or exceeded 90°F on 6 days. Normally, there are 9 days per summer. 

Precipitation - 11th Wettest Summer

• During the astronomical summer, Rochester International Airport received 17.81" of rain which was 5.76" wetter than the long-term average of 12.05".
• This was the 11th wettest summer.
• Below are the 20 wettest summers for Rochester, MN.

Wettest Astronomical Summers
    in Rochester, MN
      1886-2026

Rank   Rainfall     Year
----   --------     ----
 1   24.13 inches   1978
 2   22.68 inches   2019
     22.68 inches   1938
 4   22.37 inches   1986
 5   21.74 inches   1942
 6   21.17 inches   2016
 7   19.99 inches   2007
 8   19.28 inches   1990
 9   18.83 inches   1981
10   18.19 inches   1913
11   17.81 inches   2026
12   17.58 inches   1959
13   17.32 inches   1999
14   17.07 inches   1951
15   16.24 inches   2024
16   16.08 inches   2010
17   16.07 inches   1983
18   15.85 inches   1952
19   15.57 inches   2018
20   15.29 inches   1993

• 10 out of the past 13 summers have been wetter than average. This includes the 2nd wettest (2019 - 22.68"); 6th wettest (2016 - 21.17"); 11th (2026 - 17.81");  14th (2024 - 16.24"); and 23rd (2025 - 14.59").
• The wettest day occurred on July 31 and September 18 when 2.35" of rain fell. Just over 25% (26.4%) of the rain fell on just 2 days.
• Measurable rain fell on 29 days (31.2%) and trace amounts fell on another 9 days (9.7%).

Here is a breakdown of the summer rain...

• None             55 days - 59.1%
• Trace             9 days -  9.7%
• 0.01-0.09 inches  5 days -  5.4%
• 0.10-0.24 inches 10 days - 10.8%
• 0.25-0.49 inches  3 days -  3.2%
• 0.50-0.99 inches  3 days -  3.2%
• 1.00-1.99 inches  6 days -  6.5%
• 2.00-2.99 inches  2 days -  2.2%