Trent Ford, Illinois State Climatologist, provided this weather report. Fall came early in Illinois, with temperatures between 1.5 and 3.5 degrees below normal since late August (Figure 1). Nighttime low temperatures have dipped into the low 40s and upper 30s multiple times, and we set some low temperature records on Labor Day.
Unfortunately, the cooler weather also came along with very dry conditions across much of the state. Most of Illinois has been 3 to 4 inches drier than normal since late August, and a few places have had less than a tenth of an inch of rain since mid-August (Figure 2).
The extremely dry conditions have quickly depleted soil moisture and lowered stream levels across the state, including on the Kaskaskia and Sangamon Rivers. Wetter weather in the Upper Midwest has kept the Mississippi River at or above low flow north of Cairo, so far. However, very low flow on the Ohio River has affected the Mississippi River south of Cairo and may impact barge traffic as harvest ramps up.
The most recent outlooks from the Climate Prediction Center show best chances of above normal temperatures continuing throughout October, with slightly higher chances of drier conditions in October in southern and central Illinois. The outlooks for October through December also keep warmer than normal weather around through the end of the year; however, they also show closer to equal chances of above and below normal rainfall through December.
