The threat into the afternoon is mainly along and south of Interstate 80, ABC 7 Chicago meteorologist Cheryl Scott said.
Storms began crossing the Wisconsin state line about 4 a.m. Friday, and it appeared to be quite the light show in Lake and McHenry counties. The storms progressed across the area and moved through Chicago by about 8 a.m., ABC 7 Chicago meteorologist Tracy Butler said.
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A Severe Thunderstorm Watch was issued for Lake Geneva, Walworth and Kenosha Counties in Wisconsin until 4 a.m.
On Sheridan Road in Evanston, a tree fell across the road about 4:45 a.m., and heavy rain appeared to make roads slick and create standing water.
Winds between 40 and 50 mph were recorded in the Chicago suburbs, Butler said.
Over 17,000 people were without power at about 6 a.m., as the storms swept through, ComEd said.
But the rain is especially needed in the northern suburbs. Lake and McHenry counties are currently in an "extreme" drought - the worst since 2012.