Algorithm Predicts Where to Find America's Brightest Autumn Leaves

Most people don’t know exactly when autumn leaves will be their most vibrant, making it hard to plan out Instagram photo shoots. An algorithm-based fall foliage prediction map from SmokyMountains.com, however, is here to help, showing users when and where in the United States leaves will be in “peak color” throughout the fall season.

Over the next few decades, it will also likely show how climate change is messing with the autumn leaves.

The interactive map, created by SmokyMountains.com co-founder and coder Wes Melton, using several million data points from the National Oceanic and Atmospheric Administration, shows what to expect of leaves nationwide from August 27 to November 12. Each year, Melton feeds the algorithm new data on historical and predicted temperature and precipitation, together with data on historical leaf peak trends and peak observation trends. In return, the algorithm spits out 50,000 predictive data pieces, which are then used to make the map.

“The SmokyMountains.com data model continues to improve and become more accurate each year,” said Melton in a statement. “This is due to our expanding historical database and our ability to analyze past predictions versus historical trends.”

In the 2017 map below, which shows how leaf color shifts between August and November, areas with “no change” in leaf color are represented in green, “patchy” color is marked in dark yellow, and peak color is shown in dark red.

In the future, this map could look very different. Scientists predict that the prolonged warm temperatures associated with climate change will also weaken the vibrancy of fall colors and delay the changing of the leaves to later in the season.

That’s because temperature plays a big role in changing leaf colors, researchers at Appalachian State University’s biology department explain. Normally, as days become shorter in August and September, trees lose the chlorophyll that makes their leaves green and instead produce pigments responsible for turning leaves red, orange, and yellow. Cooler temperatures are a secondary cue to do more of this, and faster — as lower temperatures approach, trees quicken the pace of their colorful change.

But if global warming makes warm weather last longer, the researchers write, the changing of leaf colors will be delayed to later in the season. It’ll certainly be cooler then — but there will also be fewer hours of sunlight, which trees need to produce color pigments in the first place. Some trees, they warn, may not even respond to those later temperature cues, leaving us with less brilliantly colored leaves or no leaves at all, if the trees lose their leaves before they can change.

On Melton’s map, the effects of climate change might manifest as an unusually long period of cross-country green, followed shortly by a late, lengthy period of nation-wide brown. It’ll be interesting — and perhaps sad — to watch, over the next couple of years, how leaf patterns change as the algorithm takes in new data about our rapidly changing climate. Scheduling Instagram shoots, unfortunately, will only get more unpredictable from here.