Camping Gems - Illinois Tips Weather The Midwest is famously warm and humid in the summer and snowy in the winter. Illinois is no exception. From its average warm-season highs in the upper eighties to the winter average lows of 10 degrees, this is a place where seasons matter. For the most perfect weather, visit Illinois during the spring and fall. In the summer, try to camp near a lake or swimming pool, and in the winter always travel with chains and ice scrapers. |