Update 12:05AM CDT…
The line of showers/thunderstorms continues to move southeast at about 40 miles per hour. The western edge of the line looks like it could clip portions of Boone, Kane and Will Counties in northeast Illinois in addition to McHenry, Lake, Cook and DuPage Counties, eventually working over the remainder of southern Lake Michigan into northwest Indiana.
Just before 11PM CDT a southeastward-moving west-east-oriented band of showers and thunderstorms extended from Lower Michigan across Lake Michigan through Milwaukee to Madison, Wisconsin. The storms will reach Boone, McHenry and Lake, Illinois counties in northeast Illinois shortly after Midnight, and after that continue to move through portions of Cook and possibly DuPage counties, as well as southern Lake Michigan into northwest Indiana. The line of storms could elongate further to impact counties to the west of those mentioned.
Strongest storms will produce vivid lightning, brief heavy downpours, winds gusting over 40 miles per hour and possibly small hail. Marine interests on southern Lake Michigan should take action to evade these storms if at all possible.