May is starting out cool across Illinois. Temperatures are running 2 to 4 degrees below normal in parts of western and southern Illinois, to over 9 degrees below normal in the Chicago area (first map). The statewide average temperature for May so far is 53.4 degrees, 5.2 degrees below normal. This comes on the heels of a very warm April.
Parts of Illinois have been wet as well. Rainfall totals of 2 to 4 inches were common in the southern half of Illinois while the northern half has been drier with many areas at 1 to 2 inches and a few areas in northwestern IL with less than an inch of rain (second map).
Here are the potential rainfall totals over the next 7 days according to one long-range NWS model. As a rule of thumb, normal 7-day rainfall in May in Illinois is just over an inch. Amounts of less than an inch are forecasted over much of northern and central Illinois, making it below normal. Amounts of 1 to 2 inches are possible in parts of southern Illinois, making it near to above normal. Most of that rain is expected in the next two days as a system moves through the Midwest.
