September 2026 Climate Summary

Upper Mississippi River Climate Summary for September 2026:

Temperatures - Above Normal

During September 2026, average temperatures ranged from 61°F at Medford Taylor County Airport (AWOS) to 68.1°F at Guttenberg Lock & Dam 10, IA (COOP). Temperature anomalies ranged from 1°F to 6°F warmer-than-normal. There was a 60°F difference between the warmest and coldest temperatures in the Upper Mississippi River Valley. The warmest temperature was 94°F near Neillsville, WI on September 1 and near Theilman on September 4. Meanwhile, the coldest temperature was 34°F at Black River Falls, WI (ASOS) on September 14.

Rainfall -​ Highly Variable

Rainfall totals varied from 2.61" near Owen, WI (COOP) to 12.38" at Spring Valley, MN (COOP). Rainfall anomalies ranged from 2" drier than normal to 10" wetter than normal. The highest one-day precipitation was 8.29" near Houston, MN from September 18 to September 19.
Severe Weather - Above Normal
Convective Warnings -  Above Average There were 19 convective (severe thunderstorm, tornado, and flash flood) warnings. This was 7 warnings above the 1986-2026 longterm average of 12 warnings. This was the 8th most in a September and the most since 2019 (43 warnings - 2nd most). The greatest number of convective warnings in a September was 57 warnings in 2016. Severe Thunderstorm Warnings -  Above Average There were 13 severe thunderstorm warnings. This was 4 warnings above the 1986-2026 longterm average of 9 warnings. The greatest number of severe thunderstorms warnings in a September was 48 warnings in 2006.
Tornado Warnings - Average There was 1 tornado warning. This was the same as the 1986-2026 longterm average. This was tied for 8th most in a September with 1986, 1988, 1991, 1994, 1998, 2000, 2005, and 2012. The greatest number of tornado warnings in a September was 7 warnings in 2019. Flash Flood Warnings - Above Average There were 5 flash flood warnings. This was 3 warnings above the 1986-2026 longterm average of 2 warnings. This was the 6th most in a September. The greatest number of flash flood warnings in a September was 34 warnings in 2016.

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

La Crosse, WI

September 2026 was Warmer (20th Warmest) and Wetter (Tied for 15th Wettest) than Normal for La Crosse, WI

...September 2026 Highlights...

Temperatures - 20th Warmest

• During September 2026, the average temperature at La Crosse Regional Airport was 66.7°F. 
• This was 1.9°F warmer than the 1991-2020 average of 64.8°F. 
• This September was the 20th warmest September. 
• During the past 12 years, 6 out of the 10 warmest Septembers have occurred.
• 12 out of 20 warmest Septembers have occurred since 2004. This includes the warmest (2015 - 69.3°F), 2nd warmest (2019 - 69.1°F), 3rd warmest (2017 - 68.8°F), 5th warmest (2023 - 68.6°F), 8th warmest (2024 - 68°F), 11th warmest (2016 - 67.7°F), 14th warmest (2004 & 2021 - 67.2°F), 16th warmest (2005 - 67.1°F), 17th warmest (2013 - 67°F), 19th warmest (2025 - 66.8°F), and 20th warmest (2026 - 66.7°F). 
• Below are the 20 warmest Septembers in La Crosse, WI.

  20 Warmest Septembers
    in La Crosse, WI
       1873-2026

        Average
Rank  Temperature  Year
----  -----------  ----
  1     69.3°F     2015
  2     69.1°F     2019    
  3     68.8°F     2017
        68.8°F     1998
  5     68.6°F     2023
  6     68.5°F     1931
  7     68.3°F     1978
  8     68.0°F     2024
  9     67.9°F     1908
 10     67.8°F     1897
 11     67.7°F     2016
 12     67.6°F     1895
 13     67.4°F     1891
 14     67.2°F     2021
        67.2°F     2004
 16     67.1°F     2005
 17     67.0°F     2013
        67.0°F     1884
 19     66.8°F     2025
 20     66.7°F     2026

• The average high temperature was 74.9°F. This was 0.6°F cooler than the 1991-2020 normal of 75.5°F. 
• The average low temperature was 58.4°F. This was 4.3°F warmer than the 1991-2020 normal of 54.1°F. This was the 6th warmest.
• The warmest high temperature was 90°F on September 1.
• The coldest high temperature was 63°F on September 21 and September 27.
• The warmest low temperature was 74°F on September 4.
• The coldest low temperature was 44°F on September 23.

Rainfall - Tied for the 15th Wettest with 1992

• A total of 7.01" of rain fell.
• This was 3.38" wetter than the 1991-2020 average of 3.63".
• This was tied with 1992 the 15th wettest September.
• Below are the 20 wettest Septembers in La Crosse, WI.

  20 Wettest Septembers
    in La Crosse, WI
       1873-2026

Rank   Rainfall    Year
----   --------    ----
  1  10.87 inches  2015
  2  10.52 inches  1965    
  3  10.46 inches  2016
  4  10.01 inches  1884
  5   9.84 inches  1901
  6   9.04 inches  1934
  7   8.51 inches  1980
  8   8.10 inches  1986
  9   7.60 inches  1908
 10   7.40 inches  1946
 11   7.34 inches  1941
 12   7.15 inches  1925
 13   7.11 inches  1906
 14   7.03 inches  2010
 15   7.01 inches  2026
      7.01 inches  1992
 17   6.92 inches  2005
 18   6.86 inches  1942
 19   6.77 inches  2019
 20   6.72 inches  1972

• The wettest day occurred on September 18 when 2.20" of rain fell.
• Measurable rain fell on 14 days (46.7%) and trace amounts fell on another 4 days (13.3%).

Mississippi River at La Crosse, WI - Below Average

• During September, the Mississippi River at La Crosse had an average 7 AM stage of 5.15 feet.
• This 0.3 feet below the 1937-2026 average of 5.45 feet.
• The lowest 7 AM stage was 4.85 feet on September 8. 
• The highest 7 AM stage was 6.07 feet on September 22.

...September 2026 Records...

• September 4 - Record Warm Low - 74°F - previous record was 73°F in 1960 and 2014
• September 18 - Rainfall - 2.20" - previous record was 1.60" in 1942

...Looking Ahead to October...

• The normal high temperature in La Crosse starts off at 69°F on October 1st and falls to 54°F by the end of the month. The normal low temperature starts off at 47°F on the 1st and falls to 36°F by the end of the month. The warmest October temperature on record is 93°F on October 6, 1963, and the coldest is 6°F on October 25, 1887.
• The normal mean temperature for October is 51.7°F. La Crosse’s warmest October occurred in 1963 with an average temperature of 61.2°F, and its coldest October occurred in 1917 with an average temperature of 39.4°F.
• The normal October precipitation is 2.49". The wettest October occurred in 1881 with 12.09" of precipitation (second wettest month - only August 2007 was wetter with 13.75") and the driest October occurred in 1952 with only 0.02" of precipitation (third driest month - only November 1976 with a trace and December 1943 with 0.01" were drier). The wettest October day occurred on October 28, 1900, when 4.89" of rain fell (4th wettest calendar day). Normally, there are 2 days with thunderstorms.
• The normal October snowfall is 0.3". The snowiest October occurred in 1917 with 7" of snow. The snowiest October day occurred on October 28, 1917, when 4.7" of snow fell.

Rochester, MN

September 2026 was Warmer (14th Warmest) and Wetter (16th Wettest) than Normal for Rochester, MN

...September 2026 Highlights...

Temperatures - 14th Warmest

• During September 2026, the average temperature at Rochester International Airport was 64.2°F. 
• This was 3.1°F warmer than the 1991-2020 average of 61.1°F. 
• This was tied for the 14th warmest September with 2017. 
• During the past 12 Septembers, 5 out of the 10 warmest Septembers have occurred. 
• 16 out of 26 warmest Septembers have occurred since 2004. This includes the 3rd warmest (2023 - 66.3°F), 4th warmest (2015 - 66.2°F), 5th warmest (2024 - 65.4°F), 8th warmest (2019 - 65.1°F), 9th warmest (2005 - 64.7°F), 10th warmest (tied with 2004, 2016, and 2025 - 64.4°F), 14th warmest (2026 - 64.2°F), 15th warmest (2017 - 64.1°F), 16th warmest (2013 - 64°F), 19th warmest (2007 - 63.9°F), 23rd warmest (2018 and 2021 - 63.1°F), and 25th warmest (2008 and 2009 - 62.6°F).
• The table below contains the 20 warmest Septembers for Rochester, MN.

  20 Warmest Septembers
    in Rochester MN
       1886-2025

        Average
Rank  Temperature  Year
----  -----------  ----
  1     69.6°F     1908
  2     66.9°F     1931    
  3     66.3°F     2023
  4     66.2°F     2015
  5     65.4°F     2024
  6     65.3°F     1948
  7     65.2°F     1933
  8     65.1°F     2019
  9     64.7°F     2005
 10     64.4°F     2025
        64.4°F     2016
        64.4°F     2004
        64.4°F     1998
 14     64.1°F     2026
        64.1°F     2017
 16     64.0°F     2013
        64.0°F     1939
        64.0°F     1919
 19     63.9°F     2007
 20     63.7°F     1978

• The average high temperature was 71.8°F. This was the same as the 1991-2020 normal of 71.8°F. 
• The average low temperature was 56.6°F. This was 6.2°F warmer than the 1991-2020 normal of 50.4°F. This was the 2nd warmest. Only 1908 was warmer with an average of 57.3°F
• The warmest high temperature was 89°F on September 4.
• The coldest high temperature was 59°F on September 21.
• The warmest low temperature was 71°F on September 4.
• The coldest low temperature was 45°F on September 14 and September 23. 

Rainfall - 16th Wettest

• A total of 6.22" of rain fell. 
• This was 2.62" wetter than the 1991-2020 average of 3.60"
• This was the 16th wettest September.
• Below are the 20 wettest Septembers in Rochester, MN.

  20 Wettest Septembers
    in Rochester MN
       1886-2026

Rank   Rainfall    Year
----   --------    ----
  1  10.50 inches  1986
  2   9.95 inches  2010    
  3   9.10 inches  2016
  4   8.35 inches  2019
  5   8.08 inches  1978
  6   7.95 inches  1938
  7   7.58 inches  2018
  8   7.50 inches  1942
  9   7.40 inches  2007
 10   7.13 inches  2005
 11   7.06 inches  1972
 12   6.47 inches  1946
 13   6.41 inches  1985
 14   6.32 inches  2041
 15   6.26 inches  1965
 16   6.22 inches  2026
 17   5.99 inches  1964
 18   5.88 inches  1934
 19   5.84 inches  1973
 20   5.80 inches  2004

• The wettest day occurred on September 18 when 2.35" of rain fell. 
• Measurable rain fell on 12 days (40%) and trace amounts fell on another 5 days (16.7%). 

...September 2026 Records...

• September 4 - Record Warm Low - 71°F - Previous Record was 70°F in 2015
• September 18 - Record Rain - 2.35" - Previous Record was 1.26" in 2003

...Looking Ahead to October...

• The normal high temperature in Rochester starts off at 66°F on October 1st and falls to 50°F by the end of the month. The normal low temperature starts off at 44°F on the 1st and falls to 32°F by the end of the month. The warmest October temperature on record was 93°F on October 3, 1997, and the coldest was -6°F on October 25, 1887.
• The normal mean temperature for October is 47.9°F. Rochester’s warmest October occurred in 1963 with an average temperature of 58.1°F, and its coldest October occurred in 1917 with an average temperature of 37.6°F.
• The normal October precipitation is 2.43". The wettest October occurred in 1911 with 9.11" of precipitation and the driest October occurred in 1952 with only 0.01" of precipitation. The wettest October day occurred on October 6, 1911, when 2.85" of precipitation fell. Normally, there are 2 days with thunderstorms.
• The normal October snowfall is 0.9". The snowiest October occurred in 2009 with 7.9" of snow. The snowiest October day occurred on October 22, 1979, when 5" of snow fell.