Labor Day is almost here, and leaves in the Rocky Mountains are just beginning to change color. Parts of Oklahoma, meanwhile, won’t hit their peak reds and oranges until November.
The map provides granular, county-by-county and week-by-week predictions, showing when different parts of the country will approach peak autumnal glory, reports Brittany Anas for Forbes. It shows a few peak patches in places like Utah, Minnesota and Vermont during the week of September 20. Less than a month later, during the week of October 11, large swaths of the country, from Appalachia to western Washington State, should be at their best.
“Similar to any meteorological forecast, leaf predictions will never be 100 percent accurate,” says Smoky Mountains co-founder David Angotti in a statement quoted by Time Out’s Emma Krupp. “However, after publishing our predictive fall foliage map for nearly a decade, we are quite confident in our data sources, process and algorithm."
As Cailey Rizzo reports for Travel + Leisure, Smoky Mountains plans to improve the 2021 map’s accuracy by publishing an update in mid-September.
“Our experience combined with a scheduled mid-season update has us especially confident about this year’s predictions,” says Angotti in a statement to Travel + Leisure. “Our goal is that this data-based, interactive tool will increase the number of people that are able to enjoy peak fall in 2021.”
Smoky Mountains uses publicly accessible data, including precipitation and temperature forecasts from the National Oceanic and Atmospheric Administration (NOAA), as well as average daylight exposure, to build its predictions, wrote Nora McGreevy for Smithsonian magazine last year.
Per the United States Forest Service (USFS), the biggest factor in color change and falling leaves is length of day. Earlier sunsets and longer nights trigger biochemical processes within leaves, causing chlorophyll production to slow down and eventually stop. This removes green from the leaves, revealing colors produced by carotenoids, which create yellow, orange and brown tones. At the same time, veins that carry fluids in and out of leaves close off, trapping sugars and promoting the creation of anthocyanins, which produce red and purple colors.
Weather also plays a role in foliage color. Spells of warm, sunny days and cool but not freezing nights are ideal for creating the most red-hued anthocyanin pigments. Since carotenoids are always present in leaves, yellow and gold tones are more consistent from year to year. Soil moisture can also affect foliage, with severe summer droughts making trees begin changing color later in the year.
“The Pacific Northwest has had such an unbelievably abnormal year in terms of [its] climate,” he says. “I just don’t know what that’s going to do to [its fall colors]. But places near normal climate conditions produce great foliage in many areas. … Colorado, Wisconsin, Michigan all look great this year, and New England is always beautiful.”
Salge recently made his own predictions for the season in Yankee magazine’s fall foliage forecast. He writes that central and southern New England’s cool, wet summer seems to be causing earlier color changes in places that are typically wet, but the leaves should hold their color for a large part of the season. The Upper Midwest is also poised for a good fall for fans of colorful scenery—but drought-stricken parts of the Southeast and Mountain West may have relatively short foliage seasons.