Climate Change Shifts Timing and Color of Fall Foliage Across the East

Autumn on the East Coast is arriving with shifting patterns in how and when fall colors appear, a sign of how climate change is shaping a long-standing seasonal spectacle. While many areas across Maine, Vermont, New York and beyond still see maples and oaks blaze in oranges, reds and golds, the timing and intensity of those displays are increasingly variable. Leaves may begin to change color as early as mid-September in some years and linger into November in others, but the year-to-year rhythm is less predictable than in the past.

Leaves switch colors as temperatures cool and daylight shortens, triggering a breakdown of chlorophyll and the reveal of pigments that have been present all along. The transition is a chemical process tied to the plants’ physiology. "They’re present the whole time," says Stephanie Spera, a professor at the University of Richmond who is currently studying shifts in the fall foliage season. "They’re just masked by all the chlorophyll." However, not all trees turn red in the autumn. Some, like aspens, tend toward yellow, while others show different patterns.

Aspen trees, and also some other trees, get extra nitrogen from fungi in their roots, so they don’t need to make such a big effort to recuperate the last nitrogen from their leaf, according to Susanne Renner, honorary professor of biology at Washington University in St. Louis. For maples and oaks that lack this nitrogen boon, they must produce an energy-consuming "sunscreen" that allows the leaves to stay on the branches—and absorb more nutrients—a little longer. Evergreen species, meanwhile, have protections that help them retain needles rather than dropping entire leaves. "Their needles are really thin and covered in wax," says Spera. "And because their needles are so thin, it’s not like the big energy-intensive situation where you have a giant leaf, taking all this light."

There is no single, universal answer to how climate change will alter fall foliage, and impacts vary by tree type and region. Renner cautions that it is not possible to predict, across the board, how warming will affect leaf coloration. One constant, however, is the chemistry behind color formation. Renner notes that maple trees will continue to produce red hues regardless of temperature, because of the plant’s inherent chemistry. Yet trees also rely on cold cues to drive the shutdown of chlorophyll production and the progression to brilliant colors. "Fall colors in some regions and some years are pretty dull because the nights weren't cold enough," Renner adds. Spera echoes that temperature dynamics matter: "Without a stronger decline in temperature, the trees don't have that cue to start shutting down chlorophyll production and shutting down photosynthesis." The result can be season-by-season variability in both timing and vibrancy.

In Maine, where Spera has been studying fall foliage, the timing has shifted gradually with warmer summers. Researchers there have observed that the season has been delayed by almost a day each decade, a pattern linked to overall warmer temperatures in the preceding months. The warming trend, coupled with changes in rainfall, can also influence leaf health and color development.

Rain patterns and drought conditions further complicate the scene. Excess rainfall can promote fungal infections that mute colors, while drought can cause leaves to scorch and drop prematurely. Spera notes that drought-affected summers can lead to crisper, browner leaf outcomes and earlier leaf drop, reducing the likelihood of the dramatic color displays tourists expect. "The leaves literally crisp off the trees," she says.

All of these variables matter economically. New England’s famed fall foliage season is a major draw for travelers and contributes an estimated $8 billion to local economies. Given the shifting timing and potential changes in color intensity, experts predict that this year’s foliage could be "bright, brief and early" in some areas, following a summer marked by drought and erratic rainfall.

The mosaic of responses underscores a broader point: climate change is reshaping a natural phenomenon that has long served as a cultural and economic anchor for the region. While the chemistry of leaf color will persist, the cues that trigger peak displays—the length of nights, the depth of cold, and the balance of rainfall—are becoming less predictable. For observers and policymakers, that means more attention to regional weather patterns, forest health, and the tourism implications of a season that may arrive on the calendar at different times or with less intensity than in the past.

As winter approaches, researchers will continue to monitor how shifts in temperature and precipitation influence the timing and vibrancy of fall foliage. The lessons from Maine, New England and other tree-rich regions will help scientists better understand the complex interplay between climate and the living colors that define autumn. In the meantime, travelers planning leaf-peeping trips should consider flexible schedules and local forecasts, recognizing that peak color now may arrive earlier or later than in previous years, depending on your location and the year’s weather patterns.