Warmest September Since 1897 in Duluth

Although temperatures took a nose dive for the final few days of the month, September 2009 will be remembered as a warm one. Many locations across the Northland reported 20 or more September days with afternoon temperature readings in the 70s and few 80s.

The Duluth Airport closed out September with an average monthly temperature of 62.0 degrees F. The Duluth record books have not seen a September this warm since 1897, which holds the all time record by half a degree. In Duluth, the 30 year normal daytime high temperature for September is in the mid 60s with the normal average monthly temperature 54.7 F. International Falls, MN recorded its 3rd warmest September, with an average temperature of 59.7 degrees F.

In comparison, the monthly average temperature at the Minneapolis/St Paul Airport was 66.5 F. 

Temperature Graphs

Duluth, MN

International Falls, MN

 Brainerd, MN Park Falls, WI

 
 

Duluth, MN Top 10
 Warmest Septembers
(1870 to 2009,
Threaded Extremes)
       Temp         Year
1 62.6 F 1897
2
 62.0 F 2009
3 61.5 F 1931
4 61.5 F 1891
5 61.0 F 1906
6 60.4 F 1908
7 60.3 F 1920
8 60.2 F 1948
9 60.1 F 1933
10 60.0 F 1940
 
September 2009 at Duluth observed two days with temperatures topping out at 80 F and 20 days with highs in the 70s; the most ever recorded in a single September. The old record was 19 days set in 1948.  Considering the entire period of record back to 1874, the average number of days in September that reach 70 degrees or higher is 8 days.

Although rare, the Duluth Airport has seen thermometer readings in the 90s in past Septembers, but none in 2009. The warmest September day since weather observations began in 1874 was September 7th, 1976 when an afternoon high of 95 degrees was reached.

Other locactions across the Northland have also experienced the warm start. NWS Cooperative Weather Observers across northern Minnesota and northwest Wisconsin reported daily maximum temperature in the 70s and low 80s through the first three weeks of September.
     

The International Falls Airport ended the month about 6 degrees above the 30 year normal, but did not make it into the top five warmest Septembers on record. Afternoon temperatures reached into the 80s twice. The warmest day in September was 19th where a high of 83 F was recorded. There were 24 days in the month at International Falls where the thermometer peaked over 70 F. This is two days short of the most occurances of 70 degree days in September; observed in 1920 and 1922.

The offical NWS Cooperative Observer at Brainerd, MN reported 26 of the 30 days in September having temperature readings in the 70s. This is double the average for Brainerd and sets a new record. Previously, the most days in September with highs in the 70s was 24 days in 1931. 
 
International Falls, MN
Top 5  Warmest
Septembers
(1906 to 2009,
Threaded Extremes)
  Temp Year
1 62.6 1920
2 59.8 1922
3 59.7 2009
4 59.2 1940
5 58.5 2002,1948
Contributing to the unusual warmth was not only the long stretch of warm daytime highs, but the accompanying mild overnight lows. At Duluth, the normal daily low temperature for the month ranges from the upper 40s in the first portion of the month to the low 40s near the end.  In contrast, the warmest night was the morning of the 9th where the thermometer bottomed out at just 60 degrees F.

The normal overnight low temperatures for International Falls run about 3 degrees cooler, due to Duluth's proximity to the relatively warm water of Lake Superior. Overnight low temperatures at International falls have ranged from 40 F on the 1st to 59 F on the morning of the 20th.
 
  
Monthly Rainfall Amounts:
Duluth's Rainfall Total for September was 1.40 inches
This is 2.62 inches below the 30 year normal

International Falls' Rainfall Total for September was 1.87 inches
This is 1.08 inches below the 30 year normal

Brainerd's Rainfall Total for September was .87 inches
This is 2.02 inches below the 30 year normal
 

Duluth, MN
Top 10
Driest Septembers

1

0.19

1952

2

0.32

1892

3

0.37

1948

4

0.68

1932

5

0.72

1939

6

0.88

1953

7

0.98

1974

8

1.00

1896

9

1.04

1893

10

1.21

1898

International Falls, MN Top 5
Driest Septembers

1

0.28

1998, 1952

2

0.69

1879

3

0.74

1918

4

0.86

1974

5

1.00

1911
 
More Climate Information
     
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 



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