A tornado warning was issued for portions of McHenry and Boone counties until 10:15 a.m. A tornado watch is effect until 4 p.m. A high wind warning is effect from 10 a.m. until 8 p.m.
Temperatures were above 60 degrees Sunday morning, making it feel more like spring, but the warm air is one of the key ingredients for the severe weather.
The greatest threat will be from 10 a.m. to 3 p.m., according to ABC7 Eyewitness News meteorologist Phil Schwarz.
The unstable weather is expected at the same time that fans will be filing into Soldier Field for Sunday's Bears game.
Soldier Field General Manager Tim LeFevour tells Eyewitness News an evacuation plan for fans is ready, just in case.
He also says flags and temporary signage at Soldier Field have been removed due to the winds.
Fans in attendance are advised obey all warnings that could come during the game.
ABC7Chicago.com will update this developing story as more information becomes available.