Severe thunderstorms capable of producing tornadoes, very large hail, and damaging winds are expected to develop across northern Illinois on Tuesday afternoon and evening, according to the National Weather Service.

Forecasters say the first round of storms could begin developing as early as 2 to 3 p.m., with the most likely window for severe weather beginning around 4 p.m. and continuing into the late evening. The primary threat is expected to last until around 1 a.m., though storms may linger overnight in parts of the region.

The NWS says an unusually warm and humid air mass for early March is moving into the area, with temperatures expected to climb into the 70s and possibly near 80 degrees south of Interstate 80. At the same time, strong winds higher in the atmosphere will create an environment favorable for powerful thunderstorms.

If storms form early in the afternoon, they could quickly become supercells capable of producing strong tornadoes, large hail, and destructive wind gusts, forecasters said.

The greatest tornado threat is expected south of a boundary near the I-80 corridor, which includes parts of La Salle, Grundy, Kendall, and Kankakee counties. In these areas, storms could produce hail larger than 2 inches in diameter, winds over 70 mph, and tornadoes, according to the weather service.

Areas north of the boundary, including DeKalb County and the Chicago suburbs, will still face a risk of large hail and damaging wind gusts, though the tornado risk is expected to be lower.

Heavy rain is also possible as thunderstorms repeatedly move across the same areas, raising the potential for localized flash flooding Tuesday evening into early Wednesday.

Before the storms arrive, patches of dense fog are occurring Tuesday morning, particularly north of I-80, as moisture increases across the region.

The storm threat could continue overnight and into Wednesday morning across far southeastern portions of the area, where additional strong winds may develop.

Forecasters urge residents to monitor weather updates throughout the day and have multiple ways to receive warnings in case severe storms develop.