What is the coldest autumn ever recorded in the Chicago area?

Dear Tom,
What is the coldest autumn ever recorded in the Chicago area?
Michael J. Kitzinger, Elgin
Dear Michael,
The answer lies at the beginning of Chicago’s weather records — Nov. 1, 1870. Chicago weather historian Frank Wachowski informed us that the city’s first full meteorological autumn, the September-November period in 1871 with an average temperature of 47.9 degrees, is the coldest of record. Runners-up were the autumns of 1872 and 1875, both averaging 48.5 degrees. Ranking as fourth-coldest was autumn 1976 at 48.6 degrees. All three months in autumn 1871 averaged below normal. The season’s highest temperature was 87 on both Sept. 4 and 5, while the lowest was 9 on Nov. 23. To date, this autumn, despite the recent cold snap, ranks only in the top 40 coldest, averaging about 50.5 degrees through mid-November.

Notice: you are using an outdated browser. Microsoft does not recommend using IE as your default browser. Some features on this website, like video and images, might not work properly. For the best experience, please upgrade your browser.