Heavy Rains in Chicago
© Robert Kozloff / Chicago TribuneA tow truck prepares to hook up a stranded car on the feeder ramp from I-90/94 to I-290 and the Congress Parkway downtown.
Those looking for some kind of a break from the heat of the last week got it overnight -- a rainstorm that dropped temperatures into the low 70s. But like the heat wave that preceded it, this rainstorm was anything but ordinary.

According to ChicagoWeatherCenter, the total rainfall at O'Hare -- 6.91 inches as of about 6:50 a.m. -- is the largest single-day rainfall since records began in 1871. The highest previous daily total was 6.64 inches on Sept. 12, 2008. And more rain is on the way.

There were rainfall totals as high as 7 inches as the storm moved noisily through the Chicago area after midnight, resulting in flash flood warnings from the National Weather Service and enough flooded roads and highways to make life miserable for passengers headed to or from O'Hare International Airport and make a mess of traffic overnight and into Saturday morning.

The north side got the brunt of the rain, with O'Hare International airport getting 5.53 inches in two hours, according to ChicagoWeathercenter.com. Some other totals of note reported by the Weather Center: 6.41 inches in Glenview, 5.4 inches in Arlington Heights and 5.49 inches in Elk Grove Village.

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© Keri Wiginton / Chicago Tribune Rick Cavins cleans sewage out of his flooded basement on the 7800 block of West Thorndale Avenue in Park Ridge. The area was flooded after an early-morning thunderstorm.
At Little Village Academy on Chicago's West Side, the total was 7.84 inches, and the rain still hasn't left town for good. More rain is expect when some storms move in from the west.

The Metropolitan Water Reclamation District opened the locks at Wilmette and the Chicago River downtown this morning, according to the Chicago Park District. Because opening the locks causes backflow of storm runoff and sewage into the lake, precautionary swim bans were put into effect at all beaches along the Chicago lake front until test results show low levels of bacteria in the water.

The rain also flooded the Winnetka Public Library's lower level with about two feet of water, according to a press release from the library, closing the building today and tomorrow at least. No library materials were affected because the damage was primarily limited to staff areas. The Northfield Branch Library remains open.

The storm also interrupted electrical service for some. About noon, ComEd reported that about 74,000 customers were without power: 40,000 north of the city, 27,000 in Chicago, and 3,000 west and south of the city. The utility, which has about 350 crews out working to restore power, said that more than 150,000 customers experienced power outages at some point.

Among areas affected at one point was Grant Park -- where the absence of working traffic lights added to the day's traffic woes.

The forecast calls for more rain early today as another storm system moves in from the west. That will be followed by a partly cloudy afternoon with -- you guessed it -- temperatures in the 90s and high humidity.