What is the heaviest rain ever to fall in Chicago?
—Morris Pelter, Chicago
In weather records that began on Nov. 1, 1870, Chicago’s heaviest precipitation event occurred on Aug. 13-14, 1987. A total of 9.35 inches of rain came down at O’Hare International Airport — 2.86 inches on the 13th and 6.49 inches on the 14th. The O’Hare area and points northwest into Arlington Heights experienced the greatest rainfall totals. Considerably lighter rain totals were recorded elsewhere in the area, and Midway Airport registered only 2.48 inches in the same time period. Chicago’s second heaviest rain total, 8.41 inches, fell on July 22-23, 2011, also at O’Hare. Chicago’s heaviest rainfall totals have all occurred as two-day events, starting on day one and continuing through midnight into day two.