When was the last time Chicago had 80 degrees?

Dear Tom,
Several days ago my hometown, St. Louis, had an 80-degree day. When was the last time Chicago had 80 degrees?

Chuck Kennell

Dear Chuck,
The most recent 80-degree day in Chicago was a temperature of 81 on Oct. 9, 2017, at O’Hare International Airport, and Midway Airport registered 82 degrees on that same day. However, Midway also recorded 80 degrees on Oct. 20 (but O’Hare, which is Chicago’s official weather station, was only 78 degrees then).

On average, O’Hare records 81 days per year at or above 80 degrees; Midway records 86 days. The average date of the last 80-degree day is Oct. 4. Chicago’s latest-occurring 80-degree day was on Nov. 1 in 1950 when the mercury reached 81 degrees; its earliest last 80 of the season: 86 degrees on Aug. 31, 1876. (Those dates are from official records beginning in 1871.)