A fast-moving storm system that produced at least one tornado in Illinois threatened some 53m people across ten US Midwestern states.
It came out of a fast-moving storm system that was headed toward Chicago and threatened a large swath of the Midwest with dangerous winds, thunderstorms and hail, US weather officials said.
The weather service warned residents of areas threatened bythe storm "you are in a life-threatening situation .... takecover now."
At Chicago's Soldier Field, where the NFL's Bears were playing the Baltimore Ravens, officials halted play and told fans to seek shelter due to hazardous weather conditions.
The Chicago Department of Aviation, which manages O'Hare International Airport and Midway International Airport, said that as of 1.15pm (7.15pm Irish time) both facilities were at a ground stop, meaning flights were neither arriving nor departing.
Tornado warnings were in effect for parts of Illinois,Kentucky, Missouri.
Weather officials urged residents of areas with tornado warnings in place to take cover in interior,low-floor rooms of study buildings.
The NWS's Storm Prediction Center said the storm was moving dangerously fast, tracking eastward at 97kph, meaning that just looking out at the storm will not be enough to let people know when to take cover.