What is the latest occurrence for Chicago’s first fall frost and freeze?

Weather Blog

Dear Tom,
With our very mild fall this year, frost and freeze haven’t been a concern. What is the latest occurrence for the city’s first fall frost and freeze?
—Sol Greenberg
Dear Sol,
The National Weather Service does not keep statistics regarding frost, but instead uses the season’s first temperature of 32 degrees or lower to define the end of the growing season. Chicago’s “heat island” and its proximity to the warm waters of Lake Michigan delay, by about a month, the arrival of freezing temperatures in the core of the city and near the lake. On average, the season’s first freeze occurs about Oct. 3 in the outlying areas, Oct. 15 at O’Hare, Oct. 27 at Midway and Nov. 5 downtown. In official records dating back to 1871, Chicago’s initial fall freezes range from as early as Sept. 22, 1995, to as late as Nov. 24, 1931.

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