REGIONAL— This week’s summer-like temperatures likely slowed the progress of fall color changes across the North Country, but cooler weather forecast to set in over the weekend should get the color change back on track.
It’s looking to be an excellent season with particularly bright colors thanks to the plentiful rainfall throughout the summer. Barring any extreme cold snaps, this bodes well for great colors this fall, according to Brian Schwingle, DNR forest health program consultant.
While it was warm this week, September started out cooler than normal, and that prompted many maples in the North Country to hit peak color at least ten days earlier than usual.
This year’s growing conditions seem to have favored the development of anthocyanins, the compounds that produce reddish hues. Despite their name, red maples, which are the dominant maple here in the North Country, can turn anywhere from yellow to deep scarlet and everything in between during autumn. But at least so far, intense reds seem to be the dominant hue.
The North Country actually enjoys three distinct stages of color change. The maples, which can peak anywhere from mid-to-late September, followed by the aspen and birch, which typically reach peak during the first week of October. Then, in mid-October, after most leaves are down, the tamarack turn their smoky gold for autumn’s one last hurrah.
The science behind color change
The main driver of leaves changing color is the decrease of daily sunlight. However, several other factors also play into the timing and intensity of the fall color season in Minnesota, including temperature, precipitation, and tree species. Weather both before and during the season impacts fall colors as well.
Photosynthesis, or the production of sugars that depend on sunlight, begins to slow down in response to shortening days. This leads to lower levels of chlorophyll, the pigment that supports photosynthesis and gives leaves their green color. As chlorophyll fades at the end of the growing season, other colors begin to show through.
Patterns of temperature, precipitation, wind, and the timing of hard freezes can impact when fall colors peak and how long they last. These weather phenomena can only be predicted a week or so in advance, making a peak color forecast difficult.
“Brilliant fall color occurs when early fall days are sunny, nights are chilly and there is adequate rainfall throughout the growing season,” said the DNR’s Schwingle. “An earlier, lighter frost will shift peak fall color earlier in the fall color window, so pay attention to the forecast if you can be flexible with your travel timing. Regardless of conditions, there should be plenty of beautiful foliage to enjoy.”
(see below for more detailed information on the  science behind color change)
Tips for getting outdoors
If you’re thinking of a fall color road trip, let the DNR’s Fall Color Finder (mndnr.gov/fallcolor) help you plan your adventure. It’s a color-coded map that tracks the changing leaves, grasses, and wildflowers, with updates every Wednesday, just in time for Minnesotans to make travel plans for the coming weekend. State park and recreation area staff share reports and photos from their locations to give the public a good idea of what to expect.
Plan for crowds at state parks
Fall weekends are busy at Minnesota state parks, and that’s especially true of state parks on the North Shore of Lake Superior, which can be thronged with leaf-watchers in late September and early October, when colors tend to peak. You can save time by buying a state park vehicle permit online (mndnr.gov/permit) before leaving home, rather than waiting in line at a state park entry station. Arrive early for the best parking options as parking lots are often full on weekends, particularly as colors peak.
For those looking for a little more solitude, state trails, state forests, scientific and natural areas and wildlife management areas also offer beautiful views of the fall colors with smaller crowds and no vehicle permit required.
Stay overnight
Fall is a great time to camp, with cool but comfortable nights and fewer bugs. To camp at a state park or recreation area, make reservations online (mndnr.gov/reservations). In addition, first-come, first-served campsites are available in state forest campgrounds and dispersed camping is allowed in state forests. Read about all camping options on the DNR’s camping webpage (mndnr.gov/camping).

What causes fall colors?
Four main groups of biochemicals are responsible for the various yellows, oranges, reds and browns that we see in the fall: Chlorophyll, Carotenoids, Anthocyanins, and Tannins.
Each has its own color and chemistry. As the amount of these chemicals vary, they will cause subtle variations in color from one leaf to the next, or even from tree to tree.
Chlorophyll
The green color that we see on most plant leaves throughout the spring and summer is caused by a pigment called chlorophyll. Chlorophyll is one of several pigments that gather energy from sunlight in the process of photosynthesis. Chlorophyll absorbs both the blue and the red wavelengths from sunlight and reflects the green wavelengths, which is why leaves appear green. As chlorophyll production declines in the fall, other leaf pigments begin to show through.
Carotenoids
Many of the yellows and oranges we see in nature, including in carrots, are the result of carotenoid compounds. Carotenoids play a minor role in photosynthesis—they are present throughout the growing season but are only revealed when chlorophyll breaks down. You are more likely to see brilliant colors when the fall weather has warm, sunny days with cool nights between 32° and 45 °F. Look at a leaf that has been grown in the shade, and you may notice it is a duller color than leaves that grew in the full sun, even on the same plant.
Anthocyanins
The reds and purples you see in the fall are caused by anthocyanins. Many things affect the exact color produced by anthocyanins, including the pH of the cell sap in the leaves. With an acid pH, anthocyanins are often red; with a more alkaline pH they turn purple-to-blue. Because anthocyanins need sugar for their creation, weather that favors photosynthesis (sugar production) is essential. Bright, sunny fall days produce the best colors. Very little photosynthesis occurs on cloudy days, and rain can actually leach the anthocyanins and carotenoids out from the leaves. Different combinations of anthocyanins and carotenoids can result in there being yellow, orange, and red leaves all on the same tree at the same time. The exact color a tree produces will vary from year to year.
Tannins
In many forests, oak trees don’t add much to the collage of fall colors. They often just turn brown, thanks to a group of compounds called tannins. Tannins are revealed when both chlorophyll and carotenoids break down in the leaves.