September is a cooler month than August in Chicago because the winter cool-down has begun, but has there ever been a year with an August cooler than September?
Alan Peterson, Cary
In weather records dating from 1871 through 2018 (a period of 148 years), it has happened only once. The 148-year average August temperature is 72.5 degrees, but in 1927 August was a chilly month, averaging only 66.7 degrees. It was the second-coldest August ever recorded. (The coolest August was 1915, with 66.5 degrees.) The 148-year September average is 65.4 degrees. September, 1927, was milder than average, with a reading of 69.1 degrees: the 20th-warmest September on record. Those back-to-back occurrences, the 2nd coldest August followed by the 20th warmest September, produced the only time August was cooler than September.