CHAMPAIGN, Ill. — The average September precipitation in Illinois was slightly above normal, alleviating some drought in northern Illinois and expanding dry areas in central and southern Illinois, according to Illinois State Climatologist Trent Ford at the University of Illinois’ Illinois State Water Survey.
September precipitation averaged 3.39 inches, 0.16 inches more than the 30-year normal. Total September rainfall ranged from more than 9 inches in northwest Illinois to less than a half inch in eastern Illinois.
Most areas of northern Illinois experienced between 125% and 300% of normal September precipitation, improving drought conditions that had persisted since early August.
Southern Illinois received between 10% and 90% of normal precipitation. The extremely dry conditions in central and southern Illinois resulted in more widespread moderate drought and abnormally dry conditions in the Oct. 1 edition of the U.S. Drought Monitor.
Temperatures
A cold front moved through the Midwest in late August, bringing Illinois its first real taste of fall air. Below-average temperatures remained for most of September, resulting in an overall statewide average temperature of 65.4 degrees, 0.8 degrees below the 30-year normal.
September temperatures ranged from the low 60s in northern Illinois to the low 70s in far southern Illinois. All but the very northeastern corner of the state was cooler than average, including parts of Putman and LaSalle counties, which were nearly 3 degrees below the long-term September average temperature.
Cool, cloudy conditions kept temperatures across the northern half of Illinois between 10 and 15 degrees below average during the second week of September.
Although temperature departures were largest in northern Illinois, the southern half of the state experienced unusually cold weather during the third week of September.
Outlooks
The first few days of October have continued the cool weather in September. However, the outlook is for warmer and drier than normal conditions prevailing in the latter part of October.
The three-month outlooks for November, December and January are still tilted toward warmer than normal conditions. Precipitation outlooks for that same period show an equal chance of wetter and drier than normal weather.