Overnight rain proved to be just enough to break a record for the most rain recorded in Chicago for the month of July, snapping a record that had stood for 122 years.
The overnight storms, which brought much of northern Illinois under a tornado watch, dropped 0.76 inches at O'Hare International Airport bringing the month's total to 9.8 inches, according to the National Weather Service.
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Heavy rainfall made its way through Thursday night and is predicted to continue through Friday morning in the wake of Wednesday's storm that left more than 150,000 ComEd customers without power.
As of 9:45 p.m. Thursday, 15,300 still remained without power, with the hardest hit areas in the western suburbs and Chicago region, said spokesman Bennie Currie.
Cook, DeKalb, DuPage, Kane, Lake, McHenry and Will counties are under a flash flood watch until 7 a.m. Friday, according to the weather service.
"It's hard to tell the exact location where things will set up," said meteorologist Mark Ratzer. "You have some places where you see 2, 3, 4 inches of rain but then 10 miles away they don't get much of anything."
Tonight's storms could bump 2011's July further up the list of the top 10 wettest months in Chicago's history, from its current spot at number 9. The wettest month in the city's history was August of 1987, when 17.1 inches of rain were recorded.
June of 1993 sits in eighth when 9.96 inches were recorded, and June of 1892 in seventh when 10.58 inches fell, according to the weather service.
Much of the area, especially in Lake County, is still recovering from the weeks deluge.
"Certainly they can't take a whole lot more without causing some pretty rapid flooding problems," Ratzer said. "The ground is saturated. There is still standing water in some areas."