Illinois 7-Day Forecast: Highs Climb From 69°F to 85°F by Late May

What changed

The NWS forecast for central Illinois (Springfield-area grid point) shows a clear warming trend through the end of May:

• Friday, May 22: High of 69°F
• Saturday, May 23: High of 78°F
• Monday, May 25 (Memorial Day): High of 82°F
• Tuesday, May 26: High of 83°F
• Wednesday, May 27: High of 83°F
• Thursday, May 28: High of 85°F

Temperatures jump 9 degrees from Friday to Saturday alone, then continue climbing into the low-to-mid 80s for the holiday week.

Why it matters

For corn that's already emerged, sustained highs in the upper 70s and 80s help accumulate growing degree days (GDDs) at a faster clip. Corn planted in early-to-mid May across Illinois could see noticeable leaf-stage progress through this stretch. Soybeans that are up and growing will also benefit from the warmth.

Mid-80s aren't extreme, but the jump from the upper 60s to the mid-80s in less than a week is worth watching — especially if soil moisture is tight in parts of the state. Evapotranspiration picks up quickly when daytime highs stay above 80°F for several days running.

What to watch next

• Rainfall: This forecast covers temperatures only. Keep an eye on precipitation outlooks — warm and dry is a different story than warm and timely rain.
• Overnight lows: How warm nights stay will affect GDD accumulation. Check your local NWS point forecast for overnight numbers.
• Extended outlook: Whether the 80s hold into early June or pull back could affect how quickly crops move through vegetative stages.

Source notes

All temperature data from the U.S. National Weather Service API, Springfield IL grid point (ILX 47,55). Forecast retrieved May 25, 2026. These are point forecasts for one location in central Illinois — conditions will vary across the state.