The National Weather Service did not immediately confirm any tornado touchdowns. But it said trained spotters reported high-rotation winds in DeKalb and Kane counties in northeastern Illinois.
There were no immediate reports of injuries, Chicago Fire Department officials said.
Wind gusts reached well past 60 mph.
Sirens sounded in Chicago from downtown to Wrigleyville.
Kristin Febor, 21 of Chicago watched the rain approach from the roof of the Marina Towers high-rise downtown along with friends.
"The wind picked up and in probably five seconds it blew (my friend) into her husband," she said. "He grabbed her and pulled her inside and we all ran down the stairs. It was like dead still and then within five seconds, ten seconds we were all blown away."
Warning sirens sent pedestrians scrambling into high-rises and train stations for shelter.
Security guards at the Ogilvie Train Station, just off the Chicago River, ushered people streaming inside away from large glass windows and into the middle of the building.
"The lightning between the buildings was looking ominous," said Michaela Nelson, 58-year-old singer from Barrington, brushing her dripping-wet hair at the station. "And then it just poured."
Fans at the Chicago Cubs and Houston Astros game were evacuated from Wrigley Field's stands into the stadium concourse as tornado sirens blared throughout the city.
Fans got quite a show, but not the one they paid for. It was 6 p.m., and dark, ominous clouds rolled in and the skies opened up. Fans got drenched as the ground crews rolled out the tarps. That was just the beginning. Tornado warnings blared out later, and the fans were evacuated, told over the public address systems to move inside to the stadium's concourse. Some fans say it was a little scary.
"They had the alarm going on, and it was the windiest and scariest thing we have seen," said Cub fan Ann Fischer.
"Got so black, and they started to put the tarp down. We were sitting for about a half hour. We thought it was going to stop and we were going to continue on. Then all of a sudden, we could not see across from us," said Cub fan Janet Janowicki.
"We saw people start coming down the aisle. We went looking for our children here, and the next thing you know, everybody started pushing and shoving," said Cub fan Manny Hernandez.
The Cubs were losing to Houston 2-0 when the game was delayed. The game delay lasted three hours and then play was restarted.
"I've never seen anything like it. This is unprecedented," said Bob Sejnoha of Algonquin, who was at the Cubs game. "I don't think it's ever happened at Wrigley."
There was also widespread damage in Chicago and the suburbs, where trees and power lines were down. Most of the damage appeared to be straight-line wind damage, though lightning also has accounted for some damage.
Damage caused by falling trees to homes and cars was also reported in the city and south suburbs.
In Chicago, the Department of Streets and Sanitation had mobilized crews in all 50 wards to scout for damage. Please call 311 with any weather-related damage to report in the public way.
Major damage was reported in Griffith, Ind., with roofs blown off homes and signs torn from businesses. Griffith's city council president Rick Ryfa said a shelter had been set up for residents at Franklin Elementary, 200 Griffith Blvd. and it would be open overnight Monday. A hotline was also available at (219) 924-7503.
"We have gas leaks, power lines down, tree limbs all over the place - there are buildings that have had their windows blown out. I don't know if there was a tornado that came through, but it certainly had the force of one," Ryfa said.
Ryfa said as of 10 p.m. he had heard no reports of injuries.
In west suburban Addison, ABC7's John Garcia reported downed trees, power lines, light poles and signs. A live power line was flaring up across Lake Street in Addison.
In Bensenville, a tree fell across a Grand Ave., and a car crashed into it.
Lightning struck a high school in St. Charles and started a barn fire in Batavia.
"We have a significant amount of damage," said St. Charles Supt. Don Schlomann. "We have a lightning strike and some wind damage it appears as well. We are trying to make an assessment as to whether or not we have structural damage. But clearly, probably the school will be closed. Although we don't have a lot going on, but the school will be closed for the next day or two as we make an assessment as to how much damage has been done to the building."
Schlomann said it was difficult to assess the damage Monday night, as there was no power. He said the fire department was assisting with lighting but that it would be easier to examine in daylight.
"Power lines are down here. We have had to turn off all the gas to our building because we had gas leaks as well given to the damage to some of our units on the roof, big holes in the roof from the lightning strike, enough that a bunch of the rain is coming through into our flooring," Schlomann said.
Commonwealth Edison says as of 10:30 p.m. 200,000 customers were without power. Seventy-five thousand west suburban customer were without electricity as were 25,000 city customers and another 100,000 were scattered throughout the Chicago area.
Those without power are asked to call 1-800-EDISON1 to report the outage.
A ComEd spokesman said that getting power restored to all customers would be a multi-day restoration.
"One thing we do want to stress to our customers is our crews will be out in the field working around the clock to restore them as quickly and safely as possible. But we do stress to have some patience because this is going to be a multi-day restoration," said ComEd spokesman Joe Trost.
O'Hare International Airport's arrivals and departures were entirely suspended around 9 p.m. Passengers were also evacuated to lower-level terminals due to the tornado warnings.
Travelers who had already boarded airplanes were taken off as the storm struck, then led to the lower levels as a precaution.
"It was pretty cramped down there, the whole terminal was down there," said George Wickens, 50, of London, who was trying to travel to Florida with his family. "I don't think anything will be getting out of Chicago tonight."
The storms did not cause any damage or injuries at O'Hare or Midway Airport, said Department of Aviation spokesman Gregg Cunningham.
Delays at O'Hare averaged about an hour as of 10 p.m. At Midway, delays averaged about 90 minutes, Cunningham said.
The Associated Press contributed to this report.