What All This Wet Weather Does To Illinois’ Leaf Colors

If there's one thing Northern Illinois residents take seriously every fall, it's the changing leaves.

We watch the trees, check the forecasts and start planning those fall-color drives. So with all the wet weather we've had lately, have you thought about what is all this rain going to do to our fall colors?

As it turns out, it's a little more complicated than just saying, "Lots of rain means lots of pretty leaves."

Northern Illinois has had a strange weather year. The Illinois State Climatologist says the state had its eighth-wettest summer on record, although conditions varied considerably around the state.

Rockford has also had a very wet September. One Rockford-area weather station recorded nearly 8 inches of rain through September 29th, which is more than twice the normal September rainfall.

aerial photography of gray concrete road between assorted-color trees

So What Does All This Mean For Trees In Northern Illinois?

According to experts at the Morton Arboretum, fall color depends on a combination of factors, including rainfall, temperature and sunlight. Adequate moisture, bright sunny days, and cool nighttime temperatures can help produce brighter, longer-lasting colors.

But there's a catch. Warm, cloudy and rainy weather during the actual color-changing period isn't necessarily what we want.

The National Weather Service says the best conditions for brilliant fall colors are generally warm, sunny days and cool (but not freezing) nights.

And 2026 has another wrinkle. Morton Arboretum scientists say the drought that affected the region earlier this summer would normally encourage earlier color, but significantly above-average rainfall over the past 90 days has offset some of that. They're also watching a strengthening El Niño, which could bring warmer-than-average temperatures and potentially delay and/or shorten up the fall-color season.

yellow, red, and green fallen leaves

So, Our Recent Rains Shouldn't Affect Things Too Much, But The Upcoming Weather Will Matter When It Comes To Leaf-Changing

For the Northern Illinois region, Morton Arboretum experts say maples generally hit their brightest color around mid-October, while oaks tend to follow later in October, with many leaves remaining on the trees into early or mid-November.

So keep watching those trees. Northern Illinois' annual color show is coming, and Mother Nature still has a few weather cards left to play.