There are definitely races every weekend of the summer within an hour or hour and a half of chicago.
Off the top of my head:
Superweek (14 races)
Memorial Day (4 races)
Elk Grove (2 races)
Downers Grove (2 races)
Winfield (2 races)
Monsters and Cobb Park (2 races)
Proctor(ITT, RR and Crit on Fri/Sat/Sun)
Elgin/Grayslake weekend (2 races)
Wisconsin state RR and crit (2 races)
A bunch of smaller races put on my shops in Madison and Milwaukee
Synopsis: one of the best areas in the country for summer racing.
Go to abdcycling.com and look at the tool on the left hand side of the page. They have more races than you can shake a stick at. To move to the next month you click on the "Month>" when you've scrolled all the way down.