The National Weather Service says two tornadoes touched down in north-central Illinois as the remnants of Hurricane Isaac created severe thunderstorms.
Marshall County Sheriff's Office spokesman Rockie Harber says the first tornado was spotted in a sparsely populated area south of Hopewell near the Illinois River.
A second tornado briefly touched down in western Marshall County. No damage was reported.
By midday Saturday, the storm had dumped up to five inches of rain in parts of the state.
Carbondale Emergency Management Department official Ron Hertter said 3.5 inches of rain fell in 90 minutes, which led to flash flooding. He said there were no reports of damage and that the water was receding Saturday night.
A tornado watch is in effect for much of southern Illinois until 10 p.m.