What is Chicago’s average temperature?

Dear Tom,
What is Chicago’s average temperature? I’m guessing it is somewhere in the lower 60s.

Thomas Youi,
Chicago

Dear Thomas,
Your estimate is much too high. Chicago’s average annual temperature (by international convention, calculated by averaging a day’s maximum and minimum temperatures in the 24-hour period from midnight to midnight, local standard time, doing this for each day of the year, then averaging all days in the 30-year period from Jan. 1, 1980 through Dec. 31, 2009) is about 50 degrees. All weather services, internationally, do it that way. At O’Hare International Airport, that average is 49.7 degrees; at Midway, 51.6 degrees. Chicago’s highest average annual temperature, in 147 official years dating from 1871 through 2017, is 54.5 degrees in 1921; its lowest, 45.3 set in 1875.