Precipitation
Average yearly precipitation for Illinois varies from just over 48 inches (1,200 mm) at the southern tip to just under 32 inches (810 mm) in the northern portion of the state. May and June are the wettest months of the year. Flooding is the most damaging weather hazard within the state. Increased warming within urban heat islands leads to an increase in rainfall downwind of cities. Lake Michigan leads to an increase in winter precipitation along its south shore due to lake effect snow forming over the relatively warm lakes. In summer, the relatively cooler lake leads to a more stable atmosphere near the lake shore, reducing rainfall potential.
Read more about this topic: Climate Of Illinois