Summer heat, drought could impact Minnesota's fall leaf outlook, DNR says

Fall color season is almost here, and the Minnesota Department of Natural Resources says several factors will determine when the leaves peak and how brilliant they'll be.

"I look at spring, I look at May temperature, I look at May precipitation," said Ben Schwingle, Minnesota DNR Forest Health Coordinator. 

This year, May brought some good news for the trees. It was dry during leaf-out, which meant less disease pressure on emerging leaves.

But the summer brought a different challenge. Minnesota had the sixth hottest summer since record keeping began over 150 years ago. 

The lack of rain can have differing effects on the trees, according to Schwingle. Most species react to drought by a delayed color change. But some species are the opposite, and they'll actually change color earlier.

Schwingle says the biggest concern is when heat and drought become severe enough to stress the trees.

"What that very extreme heat and drought does is it starts fall color a little earlier and it dampens the kind of the brilliance of like the reds and the purples that we see on like our maples, our cherries, our red oaks," said Schwingle.

That means the weather over the next few weeks will be especially important. 

But so far, the weather is trending in the right direction, with sun, cool nights, sufficient rain, and light frost.

"When you don't have that early frost, you get really warm temperatures extending into October, what that causes is, it causes this disparity in when certain species drop their leaves, like sugar maples, versus oaks, which will hold onto their leaves longer," said Schwingle.

Your best bet for vibrant colors will be outside the areas hardest hit by drought.

The DNR's Fall Color Finder is now live and updated throughout the season to help plan your leaf peeping. No state parks have reached more than 10-25% toward leaf peak yet.