August 2026 Upper Mississippi River Valley Weather Summary

Upper Mississippi River Weather Summary for August 2026:

Temperatures - Near to Warmer than Normal

During August 2026, average temperatures across the Upper Mississippi River Valley ranged from 64.7°F at Medford Taylor County Airport, WI (AWOS) to 71.9°F at La Crosse Regional Airport, WI (ASOS). Temperature anomalies ranged from near-normal to 2°F warmer than normal.  The hottest temperature was 90°F at Black River Falls, WI (RAWS) on August 12. Meanwhile, the coldest temperature was 41°F at Black River Falls, WI (RAWS) and Medford Taylor County Airport, WI (AWOS) on August 24.

Precipitation - Highly Variable

Rainfall across the Upper Mississippi ranged from 0.79" near Mantorville, MN (CoCoRaHS) to 6.42" near Dickeyville, WI (CoCoRaHS). Rainfall anomalies ranged 4" drier than normal to 3" wetter than normal. The highest 24-hour rainfall occurred near Dickeyville, WI (CoCoRaHS) when 4.21" of rain fell from July 31 through August 1.

August Severe Weather - Above Average

During August 2026, there was 25 convective weather warnings. The long-term (1986-2026) average is 20.3 warnings. There was 24 Severe Thunderstorm Warnings (tied with 1996 for the 10th most in August) and 1 Tornado Warning. At least 1 convective warning was issued on 7 days in August. The greatest warnings on calendar day was 6 warnings on August 18. This was followed with 5 warnings on August 11, 4 warnings on August 7, 3 warnings on August 21 and August 26, and 2 warnings on August 12. The most August convective warnings in a county was Fayette (IA) with 5 warnings (4 severe thunderstorm warnings and 1 tornado warning). The least convective warnings in a county were in Dodge (MN), Jackson (WI), Mower (MN), and Taylor (WI) counties with no warnings.

Below are the August 2026 climate summaries for La Crosse, WI, and Rochester, MN.

La Crosse, WI

August 2026 was Cooler and Drier than Normal at La Crosse, WI

...August 2026 Highlights...

Temperatures - Cooler than Normal

Rainfall - Below Normal

• A total of 1.92" of rain fell at La Crosse Regional Airport.
• This was 1.98" drier than the 1991-2020 normal of 3.90". 
• The wettest day occurred on August 18 when 0.60" of rain fell.
• Rain fell on 12 days (11 with measurable rain and 1 day with a trace). 

Mississippi River at La Crosse - Slightly Below Normal

• During August 2026, the average 7 AM stage for the Mississippi River at La Crosse was 5.05 feet.  
• This was 0.33 feet lower than the 1937-2026 long-term average of 5.38 feet.
• The highest daily 7 AM stage for this past month was 5.43 feet on August 15. Meanwhile, the lowest 7 am daily stage for this past month was 4.73 feet on August 12.

...August 2026 Records...

• Daily Records...
  • None

...Looking ahead to September...

• The normal high temperature in La Crosse starts off at 81°F on September 1st and falls to 69°F by the end of the month. The normal low temperature starts off at 59°F on the 1st and falls to 48°F by the end of the month. The warmest September temperature on record was 101°F on September 6, 1922, and the coldest was 24°F on September 30, 1899.  
• The normal mean temperature for September is 64.8°F. La Crosse’s hottest September occurred in 2015 with an average temperature of 69.3°F, and its coldest September occurred in 1918 with an average temperature of 54.8°F. 
• The normal September rainfall is 3.63". The wettest September occurred in 1881 with 10.87" of rain, while the driest September occurred in 1940, with only 0.29" of precipitation. The wettest September day occurred on September 6, 1884, when 5.55" of rain fell. Normally, there are 4 days with thunderstorms.
• While typically no snow falls during September, measurable snow did fall in 1942 (0.2" on September 26). 
• Valley fog is quite prevalent in the area. On average, this fog reduces the visibility to a quarter-mile or less at the airport on 3 days.

Rochester, MN
 

August 2026 was Warmer and Drier than Normal at Rochester MN

...August 2026 Highlights...

Temperatures - Warmer than Normal

Precipitation - 9th Driest

• A total of 1.24" of rain fell at Rochester International Airport.
• This was 2.88" drier than the 1991-2020 normal of 4.12".
• This was the 9th driest August and the driest since 2011 (0.96" - tied for 5th driest with 1886). The driest August occurred in 1941 when just 0.31" of rain fell.
• Below are the 10 driest Augusts.

   10 Driest Augusts
   in Rochester, MN
       1886-2026

Rank   Rainfall     Year
----   --------     ----
 1    0.31 inches   1941
 2    0.34 inches   2003
 3    0.65 inches   1949
 4    0.92 inches   1908
 5    0.96 inches   2011
      0.96 inches   1886
 7    1.03 inches   1933
 8    1.17 inches   1970
 9    1.24 inches   2026
10    1.41 inches   1950

• The wettest day occurred on August 4 when 0.40" of rain fell. 
• Rain fell on 11 days (8 with measurable rain and 3 days with a trace). 

...August 2026 Records...

• Daily Records...
  • None

...Looking Ahead to September…

• The normal high temperature in Rochester starts off at 76°F on September 1st and falls to 66°F by the end of the month. The normal low temperature starts off at 56°F on the 1st and falls to 45°F by the end of the month. The warmest September temperature on record is 100°F on September 6, 1913, and the coldest was 22°F on September 28, 1942.  
• The normal mean temperature for September is 61.1°F.  Rochester’s hottest September occurred in 1908 with an average temperature of 69.5°F, and its coldest September occurred in 1993 with an average temperature of 53.6°F. 
• The normal September rainfall is 3.60". The wettest September was in 1986 with 10.50" of rain, while the driest September occurred in 1953, with only 0.33" of precipitation. The wettest September day occurred on September 12, 1978, when 5.98" of rain fell. Normally, there are 5 days with thunderstorms.
• While typically no snow falls during September, measurable snow did fall in 1942 (0.3" on September 26) and 1961 (0.8" on September 30).