Minnesota fall colors: Will they be more vibrant this year?

MINNEAPOLIS (FOX 9) - Days are starting to get shorter, the kiddos are returning to the classroom, and the Minnesota State Fair is getting underway, which means fall is just around the corner. It also means that the deep green hue we've seen this year because of all the rain will soon turn to yellows, oranges, and reds — and then of course, brown. 

Because of that rain, this year has the potential to be a spectacular fall color season with peak colors lasting multiple weeks across the state. But the heavy rain can also have a negative effect with temperatures and rainfall in September critical to developing just how awesome the colors will be.

Why some trees are already starting to turn

The occasional tree is already starting to turn different colors in the Twin Cities, but this is likely not because of the tree assuming it's fall. Brian Schwingle, the Forest Health Program Coordinator with the Minnesota Department of Resources, says that this can and does happen in very wet years. While the additional moisture this year is very beneficial for long-term plant health coming off of three very dry years, it does equate to another year of stress on our tree canopy. But it's a different kind of stress than in drought years as trees don't battle each other for moisture, but now are battling conditions that lead to easily spreadable fungal diseases. 

Fungal leaf diseases generally kill portions of leaves (making brown spots or blotches). These spots can coalesce and turn entire leaves brown, and sometimes leaves are shed very early before they even have many leaf spots on them. Usually, fungal leaf diseases are not a concern for the tree's health, but they will make them unsightly. This year, leaf diseases are quite heavy and common on quaking aspen, balsam poplars, bur oaks in some areas, white oaks in some areas, crab apples, lilacs, and probably other species too.

Schwingle explains: "Whenever a growing season has extreme precipitation or extreme drought, we see color change on parts of some trees’ canopies. This frequently happens as early as July, and it is a distinct process from when the entire forest turns fall color. It is a response to stress, and sometimes it happens prior to branches or trees dying from whatever is hurting them. This year, fall colors appearing in summer could easily be a delayed response to severe drought damage from 2023. Drought can kick-start or promote diseases of trunks, limbs, and roots, and those diseases sometimes take a long time to develop. On the other hand, fall colors in summer might be a sign of root stress from being flooded too long earlier this year."

Will the colors be extra vibrant this year?

Fall colors in Minnesota.  (FOX 9)

A wetter and cooler summer is great for maximizing fall color potential. But it is too early to predict whether fall colors will be more vibrant this year. Schwingle says this is because the weather that most impacts the "brilliance" of fall colors — in particular, reds — occurs as the leaves are shutting down for the year, which happens in September and October. Thus far though, since Minnesota hasn't experienced extreme drought, the potential for maximum brilliance is still present in trees that haven’t experienced heavy leaf disease.

"To ensure vibrant fall colors, we want cool, clear days in September with nights that do not get below freezing," Schwingle said. 

Conditions that can drastically reduce fall color brilliance include: 

• An early hard freeze in September
• A week-long rainy/cloudy/windy weather pattern in mid- or later September
• Several days of hot/dry conditions after a few cool days.

When will colors peak in Minnesota and where will the best colors be located?

Typical peak fall color in Minnesota.  (FOX 9)

The exact timing of the most vibrant few days of color for each location cannot be predicted this far in advance, but that doesn't mean we don't have an overall general time frame. While there are many factors that trigger trees to begin to change colors, the ultimate trigger is the fading daylight hours. As long as the sun is up, trees are able to produce chlorophyll, which is how they get energy from the sun. But as daylight gets shorter, they will produce incrementally less. This process eventually gets short enough, combined with overall cooler and drier conditions, that the tree realizes fall is here and begins to go dormant for the winter. We see this transition to dormancy as leaves change colors and chlorophyll production ceases for the year. 

Because fading daily daylight hours is the primary driver of changing fall colors, we have a fairly consistent time frame for colors to change in Minnesota. It often begins in northern Minnesota not long after Labor Day and concludes in southern Minnesota around Halloween. Peak times will vary a little from year to year but are often the last few days of September in the Arrowhead, then transitioning southward with peak colors around the Twin Cities metro they often at mid-month. And then often hanging on the longest right along the Mississippi River in southeastern Minnesota as late as Halloween.

For the best colors this year, FOX 9 Meteorologist Cody Matz recommends heading north. Barring anything drastic, fall colors will be quite vibrant across the entire area this year but may be slightly more brilliant in the north. This is because the Arrowhead and the Canadian border region had rainfall closer to average this year than the rest of the area. This produces less stress for the trees and would give them a better chance to be at their peak in the fall. If you're looking for more specifics, you can never really go wrong in areas right along the peak of the low mountains from Duluth to Grand Marais in the Arrowhead — and this year has the potential to be breathtaking. 

"An earlier, lighter frost will shift peak fall color earlier in the fall color window, so pay attention to the forecast if you’re able to be nimble with your travel timing," Schwingle notes. 

Where can we find updates on the colors through fall?

FOX 9 will have one to two weekly updates on FOX9.com as peak season approaches to keep you updated and point you in the right direction. FOX 9 will also get an update from the Minnesota DNR with a press conference during the first week of September that may provide more specifics about our leafing peeping this year.