The running joke among residents of Chicago is that if you don’t like the weather, just wait an hour and it will change. This is particularly true during the spring and fall, when you may find yourself juggling back and forth between a t-shirt and sweater all day long. This erratic weather is largely due to the location on Lake Michigan. The entire northern region of Illinois is influenced by the Great Lake, which creates its own microclimate.

Spring temperatures average in the low 60’s (°F) in April and May before warming up into the mid to upper 80’s (°F) for most of the summer. A solid dose of humidity makes the mercury feel much hotter, but in general summers are very nice in Illinois, particularly in the north and around Chicago. Thunderstorms are common from June through early fall with a decent chance of tornadoes when the weather is severe enough in April and May. Illinois gets an average of 35 tornadoes each year, mainly in the spring and down south, which is the most mercurial season of the year.

Winters are certainly cold in Illinois, but really no worse than in any other northern state. Chicago gets a bad rap for having brutally cold winters, but it’s really the wind that makes it feel worse than it is. From December through February, daytime highs rarely break the 40°F mark, and winds off Lake Michigan can make Chicago live up to its name, the Windy City (which really came from the shady politics, not the weather, though). But the city doesn’t shut down, so dress warmly and prepare to slog through the slush and cold like everyone else as Chicago and northern Illinois get around 40 inches of snowfall on average each winter. Southern Illinois gets much less snow and has temperatures about 10°F warmer than the north of the state.

Best Time to Visit Illinois

There’s no doubt that the prime time for a visit to Illinois is during the summer and fall. Summer weather isn’t particularly ideal, as the hot muggy days can be very uncomfortable in July and August, but this is when most of the state’s festivals and fairs happen, with Chicago having a street fest literally every weekend invigorated with outdoor energy. Be sure to book hotels as early as possible for any visits during June to August because this is the peak tourism season.

Fall is even better than summer because the daytime temperatures drop down to the upper 70’s (°F) in late September and all through October. The skies are reliably blue and the leaves of the hardwood trees turn brilliant colors. You won’t have to worry about snow until late November, and hotel rates are typically lower during fall onward through winter and the sketchy spring season.