Friday Chicago will experience strong northerly winds along the leading edge of a cool high pressure ridge extending from James Bay, Canada, to the Texas Panhandle. Highest temperatures here will probably occur during the morning hours, with gusty northerly winds flowing out of Wisconsin and down the length of Lake Michigan holding afternoon readings mostly in the middle to upper 50s.
After a chilly overnight that could see temperatures dropping into the upper 30s at cold-prone locations early Saturday morning, the center of high pressure will drift east. Winds will pick up out of the south allowing readings to rebound into the middle 60s Saturday afternoon.
Winds continue to strengthen out of the southwest Saturday night, resulting in a relatively mild 50- to 55-degree start to the Chicago Marathon on Sunday morning. Most runners will have probably finished the race when temperatures push into the 70s by midday.