The intensity of the color show will vary depending on fluctuations in the amount of rainfall received across the region this spring and summer, said Mathews.
“Many areas of Western North Carolina have experienced a lot of rainfall throughout the year, while Asheville and points north have been drier. The drier areas should have the best fall color, while the wetter areas will be less vibrant, Mathews said.”
Mathews believes that the formation of higher levels of yellow, orange and red pigments in the leaves correlates with dry weather throughout the year. The drier the climate, the more brilliant the fall leaves tend to be, she said.
“This has been an unusually rainy spring and summer for much of Western North Carolina, which, if it continues through September and October it could mean less color, especially in the red range,” she said. Cooler temperatures and fewer hours of daylight in the autumn contribute to the decomposition of chlorophyll, the chemical that gives leaves their green color in spring and summer. As chlorophyll breaks down, yellow and orange pigments – always present in the leaves, but masked by the green of chlorophyll – are revealed, and new red pigments are produced.
Depending upon the timing of the first frost, the peak of fall color should arrive during the second week of October in the higher elevations, and during the third week of October in the mid-elevations, Mathews said. Because freezing temperatures quickly degrade chlorophyll, leaves predictably peak in color a few days after a frost, she said.
The color change should begin at the higher mountain elevations in late September and continue through mid-November in the lower levels of WNC.
Regardless of when the peak is and how intense the hues are, visitors can always find good fall color somewhere in the WNC mountains, Mathews said.
“We have more than 100 tree species in the Southern Appalachians, which means not only many different colors of leaves in the fall, but also a lengthy fall color season. Some trees change and drop leaves very early, such as tulip poplar and yellow buckeye, while others linger and change later, such as oaks and hickories.”
The U.S. Northeast and Midwest have fewer tree species with good fall color, mainly sugar maples, leading to a short burst of brilliant colors, she said. “The same is true in the Western states, with color mainly coming from quaking aspens,” she said. “In Europe, again, there are many fewer tree species, meaning shorter, less diverse fall color than in the Southern Appalachians.”