Pumpkin patches, apple cider, and that crisp feeling in the air. Fall has officially arrived.
If you're looking forward to some leaf peeping, or just want to enjoy the colorful scenery that autumn brings, here's when you can expect to see those leaves change.
The main driver behind the changing leaves in the fall is shorter days.
Less sunlight causes chlorophyll, the green pigment in leaves that gives them their color, to break down. As it does so, remaining compounds become more visible, exposing the true colors of the leaves.
As this is taking place, the tree itself goes through its own changes. To protect its limbs from the cold winter ahead, deciduous trees will cut off their leaves from water and nutrients.
Once this occurs, leaves begin to shrivel and break off from their stems, falling to the ground.
In the fall, of course!
But there are a number of factors that contribute to exactly when this change takes place.
Generally, the farther north you travel in the fall, the shorter the day becomes. The shorter the day, the faster this process can occur and the sooner you’ll run into some vibrant vegetation.
However, weather also plays an important role in this. Depending on conditions such as recent temperature, cloud cover, and how much rain has fallen, this can vary year-to-year by a couple of weeks.
Fortunately for us, scientists have gotten better at predicting when we can expect to see the most vibrant colors.
David Angotti, founder of the website SmokyMountains.com, developed a model that does just that. Using millions of pieces of data that include temperature, precipitation, historical trends, and more, the complex algorithm forecasts when peak foliage will take place each year.
"In order to accurately predict fall, our model ingests a multitude of data sources including historical precipitation, NOAA precipitation forecasts, elevation, actual temperatures, temperature forecasts, and average daylight exposure to develop a baseline fall date for each county in the continental United States", Angotti explains.
"Next, the model consumes hundreds-of-thousands of additional data points from a variety of government and non-government sources and layers this data over our own historical data from past years. Finally, with a high degree of accuracy, the algorithm produces nearly 50,000 date outputs indicating the progression of fall for every county in a graphical presentation that is easy to digest."
We've already seen the change begin to take place in much of the Rockies, Great Lakes, and New England. As we close the month of September, we can expect those areas to approach their peak while the Northeast and Midwest begin to see patchy color.
Fall is in full swing by early October with places like the Mid-South and parts of the Plains starting to see the change. By the middle of the month, many areas across the country are seeing peak conditions.
In November, almost everyone in the U.S., except for the Deep South, will have passed their peak and seen their leaves hit the green.
Angotti says that while no model is perfect, his model's accuracy has improved over time.
"Since the fall foliage map is based on meteorology and predictive patterns, the precise moment Mother Nature produces peak fall is difficult to predict. While the refinement of our algorithmic model over the past eight years has helped us achieve reliable results, accurate meteorology predictions are sometimes elusive and never 100% accurate.
He adds, "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."
So while science can take some of the mystery out of Mother Nature, nothing can take away the beauty that she brings this time of year.
Try it for yourself and see when you can expect peak color!