Dear Tom,
What is the average date of the first frost?
Paul Garamoni, Libertyville
Dear Paul,
A general frost and freeze is not expected in the area in the next several days, but we all know the deep chill of autumn is inexorably approaching.
The National Weather Service does not track frost, but the first autumn occurrence of 32(degrees) is taken as the end of the growing season. That varies greatly across northeast Illinois.
The combination of the city heat island and proximity to the autumn warmth of Lake Michigan creates a sharp seasonal freeze gradient from the Loop to the metropolitan outskirts that is unlike anywhere else in the Midwest. The average first freeze date ranges from Oct. 10 in the Fox Valley to Oct. 13 at O’Hare, Oct. 24 at Midway and Nov. 4 at the Loop lakefront.
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Tom Skilling is chief meteorologist at WGN-TV. His forecasts can be seen Monday through Friday on WGN-TV News at noon and 9 p.m.
WGN-TV meteorologists Steve Kahn, Richard Koeneman and Paul Dailey plus weather producer Bill Snyder contribute to this page.
