Has September ever been warmer than August in Chicago?

Dear Tom,
Has September ever been warmer than August in Chicago?
Phyllis Stedry, Berwyn
Dear Phyllis,
It is a rare occurrence and it hasn’t happened in 92 years, but September has been warmer than August in five years. In Chicago’s official temperature records from 1871 through 2018, a period of 148 years, September was warmer than August in 1884, 1891, 1897, 1915 and 1927.
In every one of those five years, August was a cool month followed by a September that was considerably warmer than normal. August’s average temperature in the period 1871-2018 was 72.5 degrees, and each of the five Augusts (listed above) had average temperatures in the middle or upper 60s. September’s average temperature in the period 1871-2018 was 65.4 degrees, and each of the Septembers in those five years had average temperatures in the upper 60s.

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