What month, on average, is Chicago’s hottest month? I

Dear Tom,
What month, on average, is Chicago’s hottest month? I believe it is July.
Tommy Mahl, Waukegan
Dear Tommy,
In weather records dating from 1871, Chicago’s hottest month is July, with an average temperature of 73.9 degrees. That is followed by August, whose average temperature is 72.5 degrees; and then by June, with an average temperature of 67.8 degrees. (Monthly averages are calculated by summing the daily highs and lows in the month and then dividing by the number of entries.)
The hottest July (and, in addition, the all-time hottest month) was in 1955, with an average temperature of 84.0 degrees. Nineteen days that month saw temperatures of 90 degrees or higher. The hottest August was in 1947, with an average temperature of 82.9 degrees. And the hottest June was in 1933, with an average temperature of 76.2 degrees.

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