The worst of the heavy thunderstorms have left the Chicago area, but the rain they left behind is resulting in flood warnings throughout northern Illinois.
A flood warning remains in effect for northern Cook, southern Lake, Lee, DuPage, DeKalb, southeastern Ogle and Kane counties until Monday, according to the National Weather Service.
Creeks and small streams continued to rise Sunday evening from heavy rainfall earlier this afternoon, the weather service said. Water levels on streets and viaducts, and in flooded fields and other low-lying areas will slowly subside overnight. Runoff from the excessive rainfall will cause flooding to occur.
Some areas expected to experience flooding include Chicago, Des Plaines, the DuPage Airport, Evanston, Buffalo Grove, Addison, Arlington Heights, Aurora, Barrington, Batavia and Berwyn, the weather service said.
The weather service issued a flood warning for the Des Plaines River at Riverside, effective Monday morning to late Tuesday night.
At 7:45 p.m., the river was at 6.6 feet. Flood stage is 7 feet.
The river is expected to rise above flood stage by Monday morning and continue to rise near 7.5 feet by early Tuesday morning. The river will fall below flood stage by Tuesday evening, the weather service said.
The weather service reported that Carol Stream got an inch of rain in 15 minutes Sunday.
Other reports from the weather service include: 58 m.p.h. winds at the DuPage Airport; 1.52 inches of rain in Bartlett; 3.12 inches of rain in Elburn; 2.92 inches of rain in St. Charles; 2.26 inches of rain in DeKalb; flooded streets in Carol Stream, Evanston, Northbrook and Skokie; funnel clouds in Kankakee and Herscher.
The two lines of thunderstorms that hit the area spawned tornado warnings in Kankakee County and severe thunderstorm warnings in much of the rest of the area as the heavy weather moved across Iowa and Illinois since early this morning. The severe thunderstorm watch that was instituted about 9:30 a.m. this morning expired about 4 p.m., along with a tornado warning and watch in northern Indiana.
The storm was responsible for over 450 cancellations as of 8:45 p.m. Sunday at O'Hare International Airport, and some flights were delayed 1 hour or more, the Chicago Department of Aviation said. There were also delays of 30 to 40 minutes at Midway International Airport.
The storms included high winds -- a 75 m.p.h. gust was reported in Granville in Putnam Count -- that the National Weather Service said were of "destructive hurricane force" and lots of lightning. WGN TV meteorologist Mike Hamernik said it was perhaps the most lightning-prolific storm of the season.
According to weather service meteorologist Charles Mott, the storm's cause was a warm front from the south banging into a high pressure system with cooler air in the north. Where they meet, which happened to be across Iowa and Northern Illinois, "is where the thunderstorms occur" Mott said.
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