What are Chicago’s average dates for the year’s first and last 80-degree or higher days?
— Stephen Hawk Aurora
We passed your request on to Chicago climatologist Frank Wachowski. Using data from 1943 on, the period when the city’s official temperatures were taken at an inland location, the city has averaged 83 days a year when the mercury has reached at least 80 degrees. The average dates for the year’s first and last occurrences of 80s are April 21 and Oct. 6, respectively.
The city’s earliest 80-degree day was a high of 80 on March 3, 1974 and the latest 81 degrees on Nov. 1, 1950. On the flip-side, the city’s latest first 80 was logged on June 1, 1973 when the mercury reached 83, and the earliest end of 80-degree days took place on Sept. 10, 1996 with a high of 82.