Illlinois September was a fall-summer mix

Sept. is typically the month when summer turns to fall. This year, however, Sept. started with fall-like weather and ended with a shot of summer, according to Illinois State Climatologist Trent Ford, at the Illinois State Water Survery

Sept. average temperatures ranged from the mid-60s in northern Ill. to the low 70s in southern Ill., between 1 and 4 degrees above normal. Several Ill. locations hit highs in the low 90s in the latter half of Sept., including 37 degrees in Joilet and 39 degrees in Stockton.

Overall, the preliminary statewide average Sept. temperature was 68.1 degrees, 1.3 degrees below the 1991-2020 average.

Rainfall

Rain in the first half of the month is generally welcomed by the agriculture community to help finish out soybeans and late-planted corn, but rain after mid-Sept. usually disrupts, if not delays, early harvest activity. Sept. this year worked in the opposite way, with drier conditions early and a bit more rain later in the month.

September precipitation ranged from less than half an inch in western Ill. to over seven inches in northeast Ill. The northeast quarter fo the state was one to four inches wetter than normal in Sept., while much of the rest of the state was one to three inches drier than normal.

The preliminary statewide total Sept. precipitation was 2.64 inches, 0.71 inches below the 1991-2020 average.

In cases where multiple waves of drought are broken up by wetter periods of weather, drought impacts can accumulate over a longer peiod. The Mississippi River has responded to the months-long Midwest drought with significantly reduced flow and near record low levels. Preciptiation deficits over 12 to 18 month periods cannot be made up in a month or two, but instead require exteneded wetter weather over multiple seasons.

"While a wet winter would be beneficial to improving soil, stream, and groundwater conditions, it is likely we'll be coming into spring 2024 with some moisture deficits in parts of the Midwest," Ford said.

Outlooks

The Climate Prediction Center shows higher odds of a warmer and drier than normal Oct.

For the winter forecast, the Natiional Oceanic and Atmospheric Aministration (NOAA) predicts elevated chances of a warmer than normal winter season across Ill. from the El Nino Effect. It's important to note that el Nino is an important component of seasonal climate variability in the Midwest but is only one of many important components affecting a winter season.

For more information about monthly Ill. weather summaries, current conditions, and climate, visit the Ill. State Climatolgist website, http://stateclimatologist.web.illinois.edu/.