UPDATED 07/22/11 11:12 a.m.

CHICAGO (CBS) — A round of storms Friday morning took some of the punch out of the oppressive heat of the past several days, but not without cutting power to tens of thousands.

After a steamy, overcast early morning, the sky grew dark and threatening over downtown Chicago around 10 a.m.

At that time, heavy rain was falling in Downers Grove and Park Ridge and across the northern and western suburbs. Intense rainfall hit the Loop around 10:15.

CBS 2 Meteorologist Megan Glaros says by 11 a.m., the storms had advanced to Lake and Porter counties in Indiana. They also finally provided some relief from the days of 90-plus degree heat that has hovered over the area since Sunday; as of 11 a.m., the temperature at O’Hare International Airport was only 72 degrees.

But the storms also cut power to 45,000 ComEd customers, a figure which could increase. That figure comprises about 13,000 in the northern suburbs, about 11,000 in the city of Chicago and the near northern suburbs, and several more in the western and southern suburbs, ComEd spokesman Bennie Currie said on the CBS 2 News at 11 a.m.

A CBS 2 viewer called from Lincolnwood to report that power went out around 9:30. That same area was without power for five days last week after storms knocked out service to more than 850,00 customers across Chicagoland.

As to when the customers without power will be restored, Currie said, “It’s hard to say for certain when the restoration is going to be, but we’re working to service as many of them as we possibly can today.”

More than 50 crews are out to work on restoring power, Currie said.

The number of storm-related outages this season has set a new record at 1.6 million altogether, Currie said.

Meanwhile, the National Weather Service in Chicago issued a flash flood warning for Lake and McHenry County in Illinois. The warning was lifted before noon, but some minor flooding is still possible.

By 9 a.m., portions of McHenry and Lake have received 2 to 3 inches of rain.

Local road closings have been reported.

Runoff from this excessive rainfall may cause minor flooding. The northern half of Lake and McHenry counties has received the most rainfall so far this morning and would be most at risk.

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