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Dear Tom,
Summer began June 21 and ends Sept. 22, and summer is the warmest season. Is that precise period actually the warmest part of the year in Chicago?
— Ron Santana, Chicago
Dear Ron,
Summer is certainly the warmest of the four seasons, but the warmest quarter of the year is not the 93-day period from June 21 through Sept. 22 that we traditionally consider to be summer. Recall that June 21 and Sept. 22 — usually summer’s beginning and ending dates — are astronomical events, but summer is a climatic event. A computer scan of Chicago’s 143-year temperature data base (1871-2013) reveals that the city’s warmest consecutive 93-day period — the warmest quarter of the year in Chicago — runs from June 12 through Sept. 13.
