The National Weather Service advises everyone to have a safety plan for what may be memorable storms the evening of June 22: Baseball-size hail, hurricane-strength winds.
Ed Fenelon, a meteorologist with NWS in Chicago, advises signing up for severe-weather alerts—and being ready to get to a basement.
Commuters should check for warnings before they head home, he says, and might want to stay off the road until those warnings have passed.
Both of Chicago's airports have canceled flights as powerful storms are anticipated to hit parts of the Midwest.
The Chicago Department of Aviation said Wednesday that 85 flights had been canceled at O'Hare International Airports. Schedules there were running about 30 minutes late. At Midway International Airport, 40 flights were canceled. Flights were about 20 minutes behind.
National Weather Service meteorologist Amy Seeley says high winds are expected to be the biggest threat. There could be wind gusts over 70 mph.
Meanwhile, emergency officials are preparing for severe weather.
Rich Guidice, managing deputy of operations for the Office of Emergency Management and Communications, says there are games and concerts scheduled for theevening and his office is reviewing evacuation plans for Soldier Field, Wrigley Field and a lake front park.
The threat of severe weather includes high winds, hail and the possibility of tornadoes.
Tornadoes within the city limits of Chicago are rare, but weather experts caution tornadoes can strike anywhere if conditions are right.
Forecasters predict the most severe conditions during the late afternoon and evening hours. Far eastern Iowa and northern Illinois could see "significant" tornadoes of an EF2 rating or higher. Wind gusts could be 70 mph or greater. The worst weather is expected in Chicago after 4 p.m.
The Storm Prediction Center in Norman, Oklahoma, warned that far eastern Iowa and northern Illinois could see "significant" tornadoes of an EF2 rating or higher on Wednesday afternoon and evening.
Forecaster Matt Mosier said tornadoes will be possible for about two hours in a triangle roughly from Davenport, Iowa, to Chicago to Milwaukee. Damaging winds are then expected across northern Indiana, southern Michigan and western Ohio
In all, about 98 million people could see stormy weather Wednesday in an area stretching from southern Minnesota to the East Coast.