A history of heavy rainfall on Aug. 7?

Dear Tom,
A neighbor says that since 1990, there is a history of heavy rainfall on Aug. 7. Is that true?
— Matthew, Niles
Dear Matthew,
Chicago climatologist Frank Wachowski checked the rainfall data for Aug. 7, and your neighbor’s claim appears unfounded. While there was an Aug. 7 cloudburst this year with the city officially logging 2.36 inches of rain, the only other heavy rain occurrences since 1990 were 1.31 inches in 2007 and 1.09 inches in 2001. In the 28 Aug. 7s since 1990, the city has logged measurable precipitation in 10 years, slightly higher than the normal 30 percent value for a typical August date. Currently, August is the city’s wettest month with a normal precipitation of 4.90 inches. Since 1990, four years rank in the 11 wettest Augusts: 2001 (2nd) — 12.25 inches, 2007 (4th) — 9.70 inches, 2002 (9th) — 8.06 inches and 1990 (11th) — 7.75 inches.

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