What is the highest temperature that has ever occurred in Chicago when it was raining?

Dear Tom,
What is the highest temperature that has ever occurred in Chicago when it was raining? This isn’t a wintry question, but it has been on my mind for quite some time.
— Samantha Golus
Dear Samantha,

Indeed, it’s a summer question, but here’s your answer: June 20, 1988, was a very hot day in the city (and, as it turned out, the summer was intensely hot as well). But on the specific day in question, the temperature soared to 104 degrees shortly after 4 p.m., but then scattered showers and thunderstorms began to develop across the area.

At O’Hare International Airport, as temperatures dropped, light rain began at 5:23 p.m., and the temperature was 91 degrees. Temperatures continued to fall into the middle 70s by 6:30 p.m. But the temperature at 5:23 p.m., 91 degrees, is Chicago’s highest temperature ever to occur when it was raining.