A record-breaking 27 tornadoes hit the Chicago area on July 15 toppling thousands of trees, crushing parked cars and leaving thousands without power.
It's the highest number of tornadoes recorded in the Chicago area in a single storm, surpassing the previous single-day records of 22 tornadoes in storms in 2023 and 2014, according to the National Weather Service.
The record on July 15 could climb higher as National Weather Service continues to survey storm damage and confirms additional tornadoes. A separate storm the day before had seven tornadoes, two of which blew through the South Side of Chicago.
"This was undoubtedly a very aggressive event, and one we don't see often," said Kevin Doon, a meteorologist at the National Weather Service's office in Romeoville.
The storms produced so many tornadoes because of conditions that meteorologists call a "ring of fire," Doon said. That's a combination of warm, humid area near the ground and cooler air higher in the atmosphere.
"It creates a lot of instability that allows a quick development of storms," Doon said.
It culminated in a powerful derecho that swept across northern Illinois on July 15, resulting in more than 7,100 reports of fallen trees in the city.
Four of the tornadoes were in Chicago: One on the Near West Side along the Eisenhower Expressway, another in West Town; a third in Chicago Lawn and West Englewood; and at O'Hare Airport.
A tornado swept across O’Hare as some passengers hunkered down underground and aboard grounded airplanes. That tornado was nearly 4 miles long, with winds up to 80 mph and a width of 250 yards, according to the weather service.
The strongest tornado left a trail of damage for 29 miles from Channahon to Matteson in the southwest and south suburbs. That tornado had peak winds of 120 mph and injured two people, according to the weather service.
It's a misconception that few tornadoes hit Chicago.
Lake Michigan can deter tornadoes from forming, Doon said, but the lake can also sometimes increase the chance of a tornado. Also, the city itself is a relatively small target and not all tornadoes cause massive damage.
"Tornadoes do happen in Chicago, and they happen more often that people think," Doon said.
Meteorologists are getting better at confirming tornadoes — another reason the July 15 storm broke the tornado record. The weather service used to rely on public damage reports, but can now use improved satellite and radar technology to confirm tornadoes.
"Some of them are so short and some are so weak, about 5 to 10 years ago it would be hard to identify them," Doon said.
