Dear Tom,

The latest-in-the season 100-degree temperature ever recorded in Chicago was on Wednesday, Sept. 7, 1960. I seem to recall an early September heat wave in 1985 where the official high at O’Hare was 99 degrees on September 7. What was Midway’s high that day?

Thanks,
Greg Buck
St. Charles

Dear Greg,

Chicago has officially hit triple-digits twice on September 7, first in 1939 at the University of Chicago site and again in 1960 at Midway Airport, the latest-in-the-season occurrences for Chicago. Checking the record books, the official high on September 7, 1985, was a sweltering 99 at O’Hare. We asked Chicago weather historian Frank Wachowski to check the Midway stats for that day and he found the high there was just 95 degrees. Wachowski attributed Midway’s lower temperatures that day to more persistent cloudiness, with fewer clouds at O’Hare Airport allowing the mercury to climb to 99 degrees.