Dear Tom,
You mentioned that last summer the city recorded only four 90s. Has there ever been a summer without any?
— Max Friedman
Dear Max,
Only once in Chicago’s weather history dating from 1871 has the city experienced a summer without a single 90-degree day, and that was in 1875. The highest readings that summer were 89 degrees on June 11 and 88 degrees on July 15. However, the city’s official thermometer in 1875 was located downtown and close to Lake Michigan, and it is almost a certainty that readings reached 90 degrees at inland locations.
The city’s official weather observation station was moved inland in 1942 (to Midway Airport) and then to O’Hare International Airport (1980). The fewest number of 90-degree days logged at the inland stations was two in 1979.
Recent summers have produced relatively few 90-degree days, but historic trends indicate the potential for a substantial number of 90s this summer.
