There are definitely four seasons in the Central Illinois area around Bloomington, as the region experiences its temperature extremes in the summer and winter, but has moderate temperatures in the spring and fall. The following chart indicates average daily high and low temperatures (degrees, F) by month:

   J  F  M  A  M  J  J  A  S  O  N  D
Hi                         
Lo                        

Weather is usually warm enough to avoid outerwear from mid-April or May through September. Lighter jackets are typically appropriate for March, April, October and November. Heavier coats may be needed November-Febrauary, and likely into early March. During the peak winter months, some people prefer to have hats, gloves, and scarves, although many people will use those on only the most severe days. The coldest days are in January, and snowfall can occur from late October into late March or, occasionally, early April.

Annual snowfall is in the 12-20" range, and there is often at least one snowfall of 3-4" or more. Although snow almost never closes the city streets or schools, an accompanying wind can temporarily close local roads in rural areas. Interstate highways and the Central Illinois Regional Airport usually remain open, but can occasionally close for a few hours (especially after an heavy, early morning snowfall) while drifting snow or ice is removed.

August, and possibly July, can be hot, with daily highs often in the 80s to low 90s. During those months, there may be little rainfall, yet higher humidity. The peak outdoor season, when public outdoor pools and beaches are open, is from Memorial Day (late May) to Labor Day (early September).

Spring and fall can be very pleasant, but rainfall is typical for periods in April and May, and sometimes as the temperatures change in October or November. Your best bet for ideal weather is to visit during the late spring or early fall, when humidity is low and temperatures are mild and manageable.