By mid-afternoon the cold front extended north-south along a line from eastern lake Superior through Green Bay to Madison, Wisconsin to just west of Rockford and farther south between Moline and Peoria to just west of St. Louis, MO. Temperature drops of 25 to as much as 30 degrees have occurred within a few hours of the front passing a given point, so in the Chicago area when afternoon readings have been in the middle 70s, a falloff into the upper 40s or lower 50s will be common late this afternoon and early evening.
Along with strong southwest winds gusting from 30 to 40 miles per hour, clouds will thicken and lower as the cold front approaches a given point. As the front passes to the east, along with falling temperatures, winds will immediately shift to the west and then northwest gusting from 25 to 30 miles per hour. Clouds will continue to lower and rain or scattered thunderstorms will follow.