Illinois State Water Survey
Prairie Research Institute
We wrapped up August with another pleasant weather week. Temperatures this past week ranged from the low 70s in northern Illinois to the high 70s in southern Illinois, about 1 to 2 degrees above normal. Official numbers will be released next week, but it looks like August ended just a few tenths of a degree above normal statewide, notably cooler than Augusts of 2020 and 2021. A very warm June, cooler July, and near normal August has summer average temperatures running right around the 30-year average across the state.
Rain totals this past week ranged from over 4 inches in eastern Illinois to less than a tenth of an inch in western Illinois. August ended wetter than normal in most places outside of western Illinois, and last month was the wettest on record in Freeport and the 5th wettest on record in Rockford. Meanwhile, a large swath of western Illinois was very dry last month, including only four tenths of an inch of total August rainfall at Quincy Dam. In response to worsening conditions the US Drought Monitor expanded moderate drought and abnormally dry conditions from Henderson to Pike Counties this week. On the flip side, rain in east-central Illinois allowed the Drought Monitor to remove severe drought in Champaign County for the first time in nine weeks. And Vermilion County is now drought free for the first time in 10 weeks.
Looking ahead, the next week does not look to be particularly wet, but rainfall chances are apparent later this weekend and early next week. 7-day forecasted totals are mostly less than three quarters of an inch, although there is an increasing trend in recent model runs so there could be some opportunities for moisture return to drier parts of the state. Outlooks for the second week of September still lean to warmer than normal conditions, but show near to above normal precipitation in the southern two thirds of the state.