Mayor says "shelf cloud" created 62mph winds.
The rain that started Wednesday night led to a record-breaker.
Rain totals at O'Hare International Airport reached 9.75 inches early Thursday morning, according to the National Weather Service. That swept away the previous 9.56-inch July mark set in 1889, making this month the wettest on record.
The precipitation came during a severe thunderstorm warning for northern Cook County, northeastern Kane County, Lake County and eastern McHenry County. A tornado watch also was in effect until 1 a.m.
And while a tornado never developed, high winds did quite a number in Carol Stream.
Mayor Frank Saverino said a shelf cloud formed over the town as winds blew at 62 mph. Saverino signed a disaster declaration on Thursday morning, and clean-up crews from five neighboring suburbs came to their aid to clear debris.
"You can't stop Mother Nature. We're all suffering," said Saverino. "We got wires down and I'm concerned about electricity, about maybe somebody getting electrocuted in their own backyard."
Mother Nature also put on quite a light show during the storm. The National Weather Service estimated that 68,000 lightning bolts were generated.
The area has already experienced very heavy rainfall in recent days and additional heavy rain could lead to rapid flooding. Over the weekend, 6.86 inches of rain fell Saturday, marking a single-day Chicago record set back in 1871.
The season has been particularly damaging for Lake County, which declared a state of emergency after one storm.