Below normal rainfall has continued into fall and has both expanded and worsened drought conditions across the state. Dry vegetation and crops have caused dozens of field fires over the past two weeks. Multiple rivers have hit low- or no-flow, including the Sangamon and Vermilion, and some municipalities have begun to enact voluntary water conservation measures. The short-term forecast shows dry weather will likely persist through mid-October, and longer outlooks do not show strong signs of substantially wetter weather through at least the end of October.
Drought Intensifies as the 2025-26 Water Year Begins
Very dry weather in August, September, and the first week of October caused a significant expansion and intensification of drought across Illinois. The October 7th edition of the U.S. Drought Monitor shows at least moderate drought in 86% of the state, severe drought in 43% of the state, and a small area of extreme drought in east-central Illinois.
Maps in Figure 1 show much of central and northern Illinois were 8 to 15 inches drier than normal for the 2024-25 water year (October 1, 2024 – September 30, 2025), and parts of east-central Illinois have been 10 to 13 inches drier than normal in the 2025 calendar year.
Low River Levels Across the Midwest
Drought usually affects the flow and level of small streams and creeks first, then the tributaries of our larger rivers. When dry conditions persist for weeks to months we can see low flow along our larger rivers. Persistently dry conditions have caused very low levels along many of our state’s rivers, including the Sangamon, Vermilion, Embarras, Kaskaskia, and the Illinois River.
Very low levels and flow along the Sangamon River have added to dry and warm weather to cause several central Illinois lakes and reservoirs to drop quickly. As of October 9th, Lake Decatur was 2.4 feet below the normal level and the City of Decatur has requested voluntary water conservation as the lake continues to drop.
Fire and Dust Risk
Recent rain has helped reduce field fire risk in many places. However, fire risk remains somewhat to very high, especially in central Illinois. We saw dozens of field fires across the state over the past two weeks, illustrating the continued fire risk. Extra precautions should be taken ahead of, during, and after harvest to ensure everyone stays safe considering the enhanced fire risk. You can find more information on farm fire safety here: go.illinois.edu/farmfiresafety.
Where are We Headed?
The October 7 edition of the U.S. Drought Monitor has over 86% of the state in at least moderate drought, which is up from just 6% of the state in late August. The Drought Monitor also has extreme drought (D3) in east-central Illinois for the first time since 2012.
Unfortunately, the next 7-days look to be dry once again across most of the state (Figure 3). Despite the recent unusually warm weather, the seasons work in our favor now, because our average temperatures will drop as we continue through fall and into winter, which will at least limit evaporation from streams and lakes. Climate Prediction Center outlooks for the third week of October show a return to unusually warm weather, with no strong signal of wetter weather in sight.
In summary: we expect drought conditions across the state will likely continue to worsen in coming weeks, albeit at a slower rate because of cooler weather and some beneficial rainfall in far southern Illinois.
