Two passing storms overnight dumped enough rain to make this July the wettest one in the city's history. They also knocked out power to tens of thousands of area residents and raised fears of more flooding.



The wave of storms, which spurred tornado and flood watches across the area, raised this month's rainfall total to 9.75 inches, drowning the previous record of 9.56 inches set in July 1889.



And with more rainy weather on the way, the record is expected to keep climbing, forecasters said.



"Ten inches isn't out of the question," said Andrew Krein, a meteorologist with the National Weather Service.



It could be even more.



After a lull in thunderstorm activity late this morning and early this afternoon, strong thunderstorms are expected to develop over eastern Iowa and northwestern Illinois and move into the Chicago area, the National Weather Service said in issuing a flash-flood watch effective through Friday morning. A flood warning was in effect for northern Lake County until 3 p.m.



Rain could fall at the rate of 1 to 3 inches per hour in the heavier storms and could lead to rapid flooding, the weather service said.



Areas along and north of I-88 and I-290 appear to be the most vulnerable, although areas south to the I-80 corridor also could see heavy rain and flooding, the weather service said.



At the same time, the weather service issued a heat advisory, in effect from 10 a.m. to 9 p.m. Afternoon temperatures are expected to climb into the lower to mid 90s, with high humidity leading to peak afternoon heat index readings around 105. Areas south of Interstates 88 and 290 probably will be the hottest, the weather service said.



The rainy weather also was delaying incoming flights at O'Hare International Airport an average of 52 minutes, according to the Federal Aviation Administration.



A lot of rain wasn't needed to smash the old July record.



As of early Wednesday afternoon, 9.05 inches had fallen this month at O'Hare International Airport, the official measuring station, about half an inch less than the record 9.56 inches that fell here in July 1889, according to the weather service. The city has averaged 3.51 inches of rain in July from 1871 through last year, weather service records show.



This July is now the ninth wettest month in Chicago history. The all-time monthly rainfall record is 17.1 inches, set in August 1987.



Wednesday's storms, which were accompanied by lightning and strong wind gusts, initially knocked out power to about 69,000 ComEd customers, according to the utility. But continuing rainfall overnight raised that total to about 82,000. But by 6 a.m. repair crews had reduced that number to 69,000 once again.



The outages were fairly evenly distributed across the metropolitan area. There were 17,000 in Chicago and its near west suburbbs; 20,000 in the northern suburbs, 11,000 in the southern suburbs and 21,000 in the utility's farther western service area.



More than 250 crews will be out this morning, ComEd said.



In Carol Stream, there were reports of numerous large trees downed in the area of Gary Avenue and Thunderbird Street.



Intense winds brought down trees, large limbs and power lines in a several block area about 12:30 a.m., said resident Missy Rogers. "It just lasted a few minutes, it blew through very quickly, but there is damage everywhere," she said. "Public works crews are out there now cleaning up."



chicagobreaking@tribune.com

