CHICAGO (CBS) — A tornado watch is in effect for much of the state of Indiana – including some northwest counties – as well as downstate Illinois.

The National Weather Service reports the tornado watch is in effect until 8 p.m. for Jasper and Newton counties in Northwest Indiana.

Most of the rest of the state of Indiana is also under the watch, including the Indianapolis, Fort Wayne, and Bloomington areas. But Lake, Porter and LaPorte counties closest to the Chicago area are not affected.

Much of downstate Illinois is also under a tornado watch until 8 p.m., from Iroquois County just south of Kankakee south to Salem. Springfield, Champaign-Urbana, Danville and Effingham are all under the watch.

A tornado watch means weather conditions make a tornado possible. Storm systems have been passing through central Illinois and Indiana Monday, but only light showers have been seen in the Chicago area.

A tornado warning means a funnel cloud has been sighted. Warnings will usually be accompanied by the sounding of outdoor sirens and broadcasts of the Emergency Alert System, and the Weather Service advises anyone in a warning area to move to an interior room on the lowest floor of your house or building.

No tornado warnings have been issued Monday.