July 28 Update: Chicago's Record Wettest July
The National Weather Service (NWS) reports that the 6.86" of rainfall at Chicago on Saturday, July 23, broke the record for the date of 2.79" set just last year. It also set an all-time calendar day precipitation record, surpassing the 6.64" on September 13, 2008. The 8.20" of rainfall in a 24-hour period ending 7 am CDT Saturday was below the record set on August 13-14, 1987, however.
With one week remaining in the month, the July total of 9.04" is now slightly over half an inch below the July monthly record of 9.56" in July 1889. The 0.45" of rain which fell through the first 3 weeks of the month would have made this the 3rd driest July in 140 years of Chicago records dating back to 1871.
Image (click to enlarge): Chicago area 24-hour rainfall ending 7 am CDT, July 23, 2011, from NWS; Chicago rainfall rate and accumulation, July 23, 2011, from Iowa Environmental Mesonet via NWS
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