Best time to visit Illinois is from April to May and between September and October. Temperatures ranging from 15 to 30 C and some rain in June through August are still warm enough to explore the adventures and enjoy the scenic beauty of the state. The months of September and October harbor lesser rain and carry the touristy vibe in the air. The parks are packed in tourists and the city reverberates with life. This is the perfect time to visit Illinois and soak in the beauty of autumn weather hiking the forest trails in the State parks or taking a lakeside camping adventure. Winters cover the prairie state in snow and could be the ideal time for someone who is looking to enjoy a Chilly winter vacation in Illinois. The city of Chicago welcomes tourists from around the world hosting several festivals such as the Chicago Improv, Chicago comic, and entertainment expo and Mayfest Chicago during the summer span of April through May in the country.