Forecasters have issued severe thunderstorm warnings for Lake and McHenry counties as strong to severe thunderstorms with damaging winds are expected Saturday afternoon into the evening.
The National Weather Service (NWS) initially issued a severe thunderstorm watch in effect until 7 p.m. Saturday.
The watch includes Lake, McHenry, Will, Kane, Cook, DeKalb, Boone, DuPage, Kendall, Ogle, Winnebago and Stephenson counties.
The NWS said a line of strong to severe thunderstorms dropped southeastward out of southern Wisconsin on Saturday afternoon.
The primary threat area is in Chicago, along with the surrounding northern and western counties of the city as well as the Rockford area.
The NWS said around 3:20 p.m. that severe thunderstorms were located along a line extending from Hebron to Harvard to Marengo moving southeast at 30 mph.
The weather service then upgraded part of Lake County, McHenry County and Boone County to a severe thunderstorm warning.
All storms can produce lightning, soaking downpours and gusty winds.
Severe storms are capable of producing damaging winds up to 60 mph and nickel-sized hail. Damage to roofs, siding and trees are possible.
Torrential rainfall may cause flash flooding of roads, low-lying areas, fields and basements, and cause rapid stream and creek rises.
The weather service recommends residents have multiple ways to get weather warnings and use caution when driving in heavy rain.
The storms come amid hot and humid weather with peak heat indices of 100 to 110 degrees.
Additional thunderstorms may develop overnight bringing a threat for flash flooding, the NWS said.