What is the latest date for a 90(degrees) day in Chicago?
Nick Recchia, River Grove
Dear Nick,
An analysis of temperature data sets from four metropolitan locations–downtown Chicago, the University of Chicago, Midway Airport and O’Hare International Airport–reveals that Chicago’s “90(degrees) season” ends earlier near Lake Michigan because of the lake’s well-known cooling influence, and it lingers somewhat farther into the autumn at locations more than a few miles inland from the lake shore.
The date of Chicago’s latest-occurring 90(degrees) day in the Loop is Sept. 24 (91(degrees) on that date in 1891); at the University of Chicago (1 1/2 miles from the lake) it’s Sept. 25 (90(degrees) in 1933); at Midway (eight miles inland) it’s Oct. 6 (94(degrees) in 1963); at O’Hare (12 miles from the lake), Oct. 6 (91(degrees) in 1963).
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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.
Write to: ASK TOM WHY, 2501 Bradley Pl., Chicago, IL 60618 or asktomwhy@wgntv.com (Mail volume precludes personal response.)
