The official start of autumn is a few weeks away and heavy spring and summer rainfall could mean a strong year for fall colors around the state, according to the Department of Natural Resources.

The peak time to enjoy those gorgeous red and orange leaves in St. Paul will be between approximately Oct. 19 and 23, according to the DNR’s map. Yellow colors will likely peak here a little earlier in the month. Colors will begin to peak up north, along the Canadian border and the North Shore, in mid- to late-September.

An Oct. 5 projection, based on past trends, of fall leaf color across the state. (Courtesy of the Minnesota Department of Natural Resources)

Last year, a particularly warm and dry September hurt the timing and intensity of fall colors, forest health specialist Brian Schwingle during a news conference Friday, but this year’s wet weather has been quite helpful for the state’s plant life. The only downside of all the rain as far as fall colors go, he said, is that a slight rise in fungal leaf diseases among aspens could dampen the yellow colors in the landscape.

The weather over the next few weeks will be important in determining this year’s fall color outlook, Schwingle said.

Warmer September forecasts tend to push peak colors a few days later. Light early-season frosts can speed up the intensity, but too harsh of a freeze can cause trees to drop their leaves entirely. Tree species also respond differently: Oak trees’ colors, for example, tend to vary more with temperature, while sugar maples are more resistant.

But in fact, the top predictor of fall colors isn’t rain or temperature, he said — it’s daylight length.

As the days get shorter, plants slow down photosynthesis, the process by which they derive energy from sunlight. This means they produce less chlorophyll, a green pigment that helps with photosynthesis — and therefore, red, orange, yellow and brown colors produced by other plant compounds are revealed, Schwingle explained. This, he said, is why the DNR’s fall color predictions are fairly reliable year to year.

Starting next week, the DNR will also send out a weekly newsletter with the latest conditions and tips to enjoy peak colors, which you can subscribe to at mndnr.gov/fallcolor.

Around the state, park staff report fall color conditions weekly or every few days, spokesperson Sara Berhow said, and real-time updates are posted to the DNR’s website. The DNR website also provides information for visiting or camping at state parks and forests, recreation areas, and scientific and wildlife management areas during your search for fall colors.

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