Hurricane Irene isn't the only storm threatening the U.S. -- Illinois and Indiana may also be hit by severe thunderstorms or even tornadoes on Tuesday.

The National Weather Service warned that the Chicago metropolitan area and parts of northern Illinois and Indiana could experience storms with winds in excess of 60 miles per hour, quarter-sized hail, drenching rains and frequent cloud-to-ground lightning, Reuters reported. Isolated tornadoes are also possible.

The storms are expected pass through in the morning and again in the late afternoon and evening. More thunderstorms are likely on Wednesday, but they aren't expected to be as severe.

The warning covers 18 counties in Illinois and five counties in Indiana. Severe thunderstorms may also hit the Eastern Shore region of Maryland and Virginia on Tuesday.