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Dear Tom,
What is the warmest day Chicago has ever had?
—12 year old Marc Johnson, Western Springs
Dear Marc,
In weather records beginning on Nov. 1, 1870, the highest temperature ever recorded in Chicago occurred on July 23, 1934, at Midway Airport, when the thermometer hit a sizzling 109 degrees. Although accurate, it was not Chicago’s highest official temperature because Midway was not the official weather site at that time. The University of Chicago site, located about one mile from Lake Michigan, was official and recorded a high of 94, its temperature cooled by an afternoon breeze off Lake Michigan. Using average daily temperatures as measured by the average of the day’s high and low temperatures, Chicago’s hottest day occurred on July 30, 1916: The high/low temperatures were 102 and 84, averaging 93 degrees.