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Frosty Morning on September 24, 2002
Widespread frost occurred across much of Minnesota on September 24. Cold Canadian high pressure brought clear skies and
frosty temperatures across Minnesota. Most minnimum temperatures in northern Minnesota were in the 20's. Across central and
southern Minnesota low 30's were common. Hutchinson had a record low of 30, breaking the old record of 32 set back in 1976.
However, the Hutchinson record begins in 1957. Embarrass had a low of 21 degrees but the cold spot was Tower with 19 degrees.
Despite the fact that official low at the Twin Cities International Airport was 39 degrees, many people in the Twin Cities
woke up to frosty lawns. At the University of Minnesota St. Paul Campus, the low was 35.6 degrees at six feet above the
ground. Six feet is the typical height to measure temperature. Near the ground at the St. Paul Campus the low was 33 degrees.
The Southern Research and Outreach Center, University of Minnesota Waseca noted:
"The frost was rather hard and general for the season's first frost. Temperatures remained below 32 degrees for more than
4 hours and bottomed out at 30 degrees. The normal first frost date (for Waseca) is September 29."
Listed below is some research on frost at the official site for temperature readings at the Minneapolis St. Paul Airport.
Until 1960, official Twin Cities max/min temperature observations were taken on rooftops ranging from 32 to 105 feet above grade. Given that freezing temperatures can result from a fairly shallow layer of cold air, I will use only the last 42 years of Twin Cities airport data (1960-2001) in offering the following statistics: MSP first autumn frost statistics (1960-2001): - average first occurrence of minimum temperature <= 32 degrees F in autumn - October 5 - median first occurrence of minimum temperature <= 32 degrees F in autumn - October 3 - earliest first occurrence of minimum temperature <= 32 degrees F in autumn - September 3, 1974 - latest first occurrence of minimum temperature <= 32 degrees F in autumn - October 30, 1973 Below you will find a listing of first-frost dates (minimum temperature <= 32 degrees F in autumn) at the Twin Cities International Airport over the last 42 years. First occurrence of minimum temperature <= 32 degrees F in autumn Twin Cities International Airport 9/3/1974 9/20/1991 9/22/1995 9/23/1983 9/24/2000 9/25/1961 9/26/1962 9/26/1965 9/26/1980 9/26/1984 9/28/1967 9/30/1972 10/1/1966 10/2/1975 10/2/1981 10/2/1985 10/2/1989 10/2/1993 10/2/1996 10/3/1960 10/3/1977 10/3/1987 10/4/1968 10/5/1988 10/6/1964 10/6/1976 10/6/2001 10/7/1979 10/8/1978 10/8/1998 10/10/1970 10/10/1971 10/10/1990 10/13/1986 10/15/1992 10/17/1969 10/17/1999 10/20/1982 10/20/1997 10/25/1994 10/29/1963 10/30/1973
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