What is Chicago’s coolest July on record?

Ask Tom Why

Dear Tom,
Your recent article about Chicago’s hottest Julys prompts my question: What is Chicago’s coolest July on record?

Calin McCarthy

Dear Calin,
In 149 years of official Chicago temperature records dating from July of 1871 through July of 2019, the coolest July occurred back in 1891 (128 years ago) when the average July temperature was a chilly 66.9 degrees. That compares to the long-term July average of 73.9 degrees. The current July average, based on the years 1981-2010, is 74.0 degrees at O’Hare International Airport and 75.9 degrees at Midway Airport.
Average temperatures in Chicago have been trending slowly upward since the 1870s due to the growth of Chicago’s urban heat island and the broad-scale effect of a moderating worldwide climate.


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