With today's high temperature at O'Hare (29°C) coming in slightly above forecast—as it has almost every day this week—I can now state with confidence that 2020's was the hottest summer ever in Chicago. By my figures, we hit an average daily temperature of 24.8°C, 0.2°C above the record set in 1955.
The string of 6 days above 32°C from the 23rd to the 28th put us over the top, so that even the weekend's milder temperatures couldn't bring us back under the line.
Oh, and this is the blog's 7,501st post since May 1998. Look for the 8,000th next July.