Two rounds of severe thunderstorms swept through the Chicago area Monday, downing trees, damaging homes and leaving hundreds of thousands without power.The National Weather Service issued its first alerts around noon on Monday, and a tornado warning followed for west suburban and southwester suburba n areas. When storms did arrive, they brought down tree limbs and flooded streets all the greater Chicago area. Over 249,000 ComEd customers were without power as of early Monday afternoon, according to a company spokesperson. The west and northwest suburbs were hit hardest. But power outages spanned the region from north suburban Evanston to south suburban Tinley Park.The storms caused serious flight delays at Chicago's airports. Delays were approaching two hours at O'Hare Airport and around 45 minutes at Midway as of 2:30 p.m., according to the Federal Aviation Administration. High water covered many area roadways, slowing traffic. Cars moving south through high water covering part of Lake Shore Drive near the Montrose Avenue exit on Monday. Tyler Pasciak LaRiviere/Sun-Times More than 200 flights had been canceled at O'Hare, according to the Chicago Department of Aviation. Midway was mostly spared, with only two reported cancellations. CTA Yellow and Purple lines reported service suspensions due to track debris.The Weather Service issued a tornado warning shortly after noon, after radar showed tornado-capable storms and a "rotation" in west suburban Downers Grove. The storm continued moving southeast at 30 mph, according to an agency alert.In Orland Park, the there were downed power lines and heavy tree damage.Guy Marino, whose family has lived in the area nearly 60 years, called the storm "catastrophically worse" than any he's been through in the area before.The high winds damaged several large trees on Marino’s property, left some of his belongings, such as bird feeders, strewn elsewhere."This is my first one of this magnitude," Marino said as he drove through Old Creek on his golf cart, surveying the damage. "We’ve never had one hit in this area this bad."Previous storms might have known down a tree or two but nothing like this, he said.“Being outside would be hazardous as these storms move through,” said NWS meteorologist Scott Baker. "When thunder roars, go indoors."Forecast models have struggled to pinpoint rainfall totals because of the hot and humid conditions, Baker said. Rainfall amounts will likely vary significantly depending on where storms develop. A downed tree blocks the road near North Sheridan Road and North Pine Grove Avenue in Buena Park, Monday, July 27, 2026.Tyler Pasciak LaRiviere/Sun-Times The storms arrived on a day when the Chicago area already was under a heat advisory Monday, with heat index values expected to range from 100 to 110. As the rains subsided, a front of cooler air was expected to move through overnight into Tuesday, bringing temperatures in the low 80s Tuesday, Baker said.Residents can call 311 to request well-being checks for neighbors and loved ones, according to the police department. Pedestrians cross North Broadway Avenue near West Argyle Street in Uptown as rain pours, Monday, July 27, 2026.Pat Nabong/Sun-Times ...read more read less