As the air chills and sunlit hours shorten each fall, trees in many regions of the United States put on a show. As leaves prepare to die and drop off trees, they turn from green to brilliant hues of orange, red and yellow.
Traveling to catch a glimpse of the country’s autumnal colors may be impossible for some this year, as restrictions in place due to the Covid-19 crisis will prohibit or limit travel into and out of some states, Natalie B. Compton reports for the Washington Post.
But for those foliage enthusiasts planning socially distanced trips—or those interested in leaf-gazing in their own backyard—a recently published interactive map can help plan for the perfect view.
For the eighth year in a row, co-founders David Angotti and Wes Melton have published an interactive map of fall foliage predictions on their tourism website, SmokyMountains.com. Using publicly accessible data, including National Oceanic and Atmospheric Administration precipitation forecasts, average daylight exposure and temperature forecasts, the pair create a color-changing map that tracks when viewers can expect fall colors to be most colorful across each United States county. The map can be accessed through their website.
Predictions are calculated in week-long increments. In a statement to Travel + Leisure’s Alison Fox and Elizabeth Rhodes, Angotti notes that the models will never predict color-changing patterns perfectly.
“[A]ccurate meteorology predictions are sometimes elusive and never 100 percent accurate,” he says. “However, the good news is that the combination of nearly a decade of experience combined with great meteorological data sources ensures we achieve a higher accuracy over time.”
As Angotti tells the Post, it’s important to keep in mind that “peak” color-changing will also look different depending on the native flora in one’s area. “There are areas of the country that don’t really have many trees that are going to change brilliant colors,” Angotti says. “I wish I could make fall happen in South Florida or in the desert, but at the end of the day, the math is basically showing when the temperature and precipitation trends would cause peak fall to occur in each of these areas.”
Trees cope with cold temperatures by slowly closing the veins that carry water and nutrients to their leaves, eventually letting the leaves wither and falling to the ground. There, they break down and help fortify the soil with nutrients, per a SmokyMountains.com statement.
As Emily Toomey reported for Smithsonian magazine last year, some leaves’ bright colors result from the breakdown of green photosynthetic pigments known as chlorophylls. When these pigments begin to recede, they expose other pigments present in the leaf. For instance, cartenoid pigments present in many leaves will turn leaves a bright yellow color. (These pigments are similar to the ones responsible for the bright oranges of carrots, squash, oranges and other fruits and vegetables.)
Some red tones in tree leaves, on the other hand, come from a pigment called anthocyanin that is produced as the leaf dies, Toomey points out. According to Harvard Forest, anthocyanin and chlorophyll together can produce brownish colors in plant leaves, while anthocyanins and carotenoids can create a vibrant orange.