Illinois in December

May through September gives you Illinois at its best. Spring brings tulips to Chicago's parks and comfortable temps in the 60s and 70s. Summer means festival season — Lollapalooza in Grant Park, Taste of Chicago, and outdoor concerts at Ravinia. Fall delivers spectacular colors along the Illinois River valley. October temperatures hover around 65°F, perfect for hiking Starved Rock's canyons or touring Springfield's Lincoln sites. Winter hits hard with lake-effect snow and subzero temps, but Chicago's museums and indoor attractions stay busy. Spring can be soggy — April averages 12 rainy days — but hotel rates drop and crowds thin out.