2025 Astronomical Summer Climate Summary

Upper Mississippi River Climate Summary for Astronomical Summer 2025: Temperatures - Near to Above Normal Temperatures

During the astronomical summer of 2025 (June 20 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 3°F warmer than normal. The hottest temperature was 97°F at La Crosse Regional Airport, WI on June 21. Meanwhile, the coldest temperature was 32°F at Sparta Fort McCoy, WI (ASOS) on September 7.

Precipitation - Highly Variable

Rainfall was highly variable for astronomical summer. Rain totals ranged from 9.63 near Lake City, MN (CoCoRaHS) to 23.42 near Dickeyville, WI (CoCoRaHS). Rainfall anomalies ranged from 3" drier than normal to 10" wetter than normal. The highest one-day precipitation was 8.64" in Decorah, IA (COOP) from August 17 to August 18.

Below are the climate summaries for the 2025 astronomical spring in La Crosse, WI, and Rochester, MN

La Crosse, WI

 2025 Astronomical Summer was Warmer and Wetter than the Long-Term Average in La Crosse, WI
 

During the astronomical summer of 2025 (June 20 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... 

Other temperature tidbits this summer...​The hottest temperature was 97°F on June 21. 

• The coldest high temperature was 63°F on September 5. 
• The warmest low temperature was 80°F on June 22. This was tied with June 29, 1931 for the warmest June low temperature. There have only been 8 days in which the low temperature was 80°F or warmer. The warmest low temperature was 81°F on July 21, 1901; July 13, 1995; and July 4, 2012.
• The coldest low temperature was 40°F on September 7.
• The temperature climbed to or exceeded 90°F on 13 days. Normally, there are 13 days in summer.  

Rainfall - Wetter-than-Average

• During the astronomical summer, La Crosse Regional Airport received 14.31" of rain which was 2.29" wetter than the long-term average (1873-2025) of 12.02".
• 8 out of the last 12 summers have been wetter than the long-term average. This includes the wettest (2021 - 21.93"); 2nd wettest (2016 - 21.73"); 22nd wettest (2018 - 16.16"); and 25th wettest (2019 - 16.52").
• The wettest calendar day occurred on July 16 when 2.21" of rain fell. 
• Measurable rain fell on 36 days (38.3%) and trace amounts fell on another 10 days (10.6%). 

Here is a breakdown of the summer rain...

None             48 days - 51.1%
Trace            10 days - 10.6%
0.01-0.09 inches 17 days - 18.1%
0.10-0.24 inches  3 days -  3.2%
0.25-0.49 inches  7 days -  7.4%
0.50-0.99 inches  4 days -  4.3%
1.00-1.99 inches  4 days -  4.3%
2.00-2.99 inches  1 day  -  1.1%
3.00 inches +     0 days -  0.0%
 

Rochester, MN  
 

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

During the astronomical summer of 2025 (June 20 through September 21), it was warmer (29th warmest) and wetter (22nd wettest) than the long-term average (1887-2025) at Rochester International Airport. 

Other temperature tidbits this summer...The hottest temperature was 90°F on June 21 and June 22. ​

• The coldest high temperature was 58°F on September 5. 
• The warmest low temperature was 75°F on June 21 and June 22.
• The coldest temperature was 41°F on September 4, September 6, and September 7. 
• The temperature climbed to or exceeded 90°F on 2 days. Normally, there are 9 days per summer.  

Precipitation - 22nd Wettest Summer

• During the astronomical summer, Rochester International Airport received 14.63" of rain which was 2.63" wetter than the long-term average of 12".
• This was the 22nd wettest summer. 9 out of the past 12 summers have been wetter than average. This includes the 3rd wettest (2019 - 22.68"); 6th wettest (2016 - 21.17"); 14th (2024 - 16.24"); and 22nd (2025 - 14.59").
• The wettest day occurred on August 9 when 3.06" of rain fell.
• Measurable rain fell on 38 days (40.4%) and trace amounts fell on another 12 days (12.8%).
• Here is a breakdown of the summer rain...

None             44 days - 46.8%
Trace            12 days - 12.8%
0.01-0.09 inches 18 days - 19.1%
0.10-0.24 inches  6 days -  6.4%
0.25-0.49 inches  4 days -  4.3%
0.50-0.99 inches  7 days -  7.4%
1.00-1.99 inches  2 days -  2.1%
2.00-2.99 inches  0 days -  0.0%
3.00 inches +     1 day  -  1.1%