October 10, 2025
4 minute read
When will the leaves turn? Here's How Scientists Find Peak Fall Colors
If you want to know where the best places to peek at leaves will be this year, climate and weather science may have the answer.
Denis Tangney Jr./Getty Images
Evan Fisher fell in love for the first time changing autumn colors looking at an old maple tree in the backyard of his childhood home in North Carolina. Ten years later, the meteorologist and geospatial analyst decided to use his professional skills to predict where he could find the brightest reds, oranges, yellows and purples each year.
Along with a college friend, Fisher began using data on temperature, daylight hours and precipitation to create a machine learning model that could predict where the first signs of fall would appear and when colors would peak across the country. In 2023, the team launched Explore autumna publicly accessible platform that can forecast fall foliage throughout the continental United States.
Fischer and other experts agree that fall foliage will appear early this year. Yellow, orange and reddish leaves can already be seen in the northeast, northwest and some central parts of the country. Peak colors gradually flow from New England and the higher elevations of the Rocky Mountains to lower elevations and areas closer to the coast. According to AccuWeather's seasonal forecast, the best fall foliage in 2025 is expected in New England, the Colorado Rockies, the Plains and the Midwest, while regions such as the Appalachians and the Pacific Northwest may see duller color or earlier leaf drop.
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Why do leaves change color in autumn?
The arrival of fall isn't just a matter of natural beauty (and billions of dollars in tourism), it also gives scientists an opportunity to study the health of trees and forests, including how climate change is affecting the aging of leaves, known as senescence.
In the fall, three main factors—day length, temperature, and precipitation—influence when the leaves of different tree species change color, how long it takes, and what bright colors. For example, lack of sunlight slows down photosynthesis, which reorganizes leaf pigments and causes them to change color. Cooler temperatures allow plants to begin to shut down. Summer precipitation increases soil moisture, making leaves more vibrant as fall approaches, while summer drought can result in dull foliage.
Each tree species reacts differently to these factors. Maple leaves, for example, get their vibrant red and dark purple colors from anthocyanins, pigments that form when sugars accumulate after growth stops in the fall. Cool nights trap these sugars, enhancing color, while warm nights deplete them, causing anthocyanins to fade and leaves to lose their characteristic fall shine. Meanwhile, research has shown that warmer conditions delay leaf loss in oak and beech, while other studies show the opposite is true for birch and poplar.
Extreme weather events such as early frosts, drought, extreme heat or precipitation also have a strong effect on the brightness and timing of leaf color, says University of Arizona plant phenologist Teresa Crimmins. Stress on trees can cause the image to become dull and, in some cases, cause the leaves to fall off without ever changing color. “It’s definitely a bummer,” she says.
This year, drought and low soil moisture will lead to shorter and duller peak foliage in parts of the Northeast, as well as the southern Great Lakes and Ohio Valley, according to AccuWeather. In the West, severe drought will result in early, less vibrant foliage.
The Explore Fall team trained its model to capture these patterns, using deep learning to process decades of temperature, daylight and precipitation data. The system classifies regions into categories ranging from “Little to no color” to “Peak color” and can adjust forecasts using satellite observations. Fisher says the model can predict the peak within three days about 80 percent of the time. “Their map looks really cool,” says Crimmins.
How climate change affects leaf color
While leaf color changes have remained stable over the past two years, data from earlier shows that peak color has occurred earlier than before, which could be “a sign of more to come,” Fisher says.
Research supports this observation: A 2023 study that used satellite data, ground-based observations, atmospheric carbon measurements, and controlled experiments to tease apart the roles of temperature, photosynthesis, and day length found that warming tends to occur before the summer solstice. make aging start earlier. On the other hand, warming after the solstice slows it down, extending the colorful season.
While the longer senescence period may seem appealing to fall lovers, the downside is that leaves have less time to photosynthesize. “Once the leaves lose their green color in the fall, they switch to producing CO2.2“And if this period is prolonged, it could become a problem” because it contributes to global warming, says ecologist Constantin Zohner of the Swiss Federal Institute of Technology Zurich, who co-authored the 2023 paper.
“Fall colors are indicators of the vitality of our forests,” says forest ecologist Andy Finton of the Nature Conservancy. A sudden change in foliage is not a good sign, he explains. “Forests provide us with clean drinking water, clean air, and opportunities for recreation and well-being.”
