One of the joys of fall is the beautiful fall foliage—the reds, oranges, yellows, and browns. How will weather affect their color? Is it a good year for pretty leaves? See our 2017 fall foliage forecast.
For the first time in years, we have a glorious fall foliage forecast! The drought has subsided, our summer was mild, and the leaves are healthy. Last year (2016), while the Great Plains and Midwest have had good rains, the East and West were dry. So, the leaf season was especially short, especially for leaf peepers in New England and the Southern Appalachians. Also, in past years, gypsy moth caterpillars attacked drought-stricken trees.
This year, the trees have been largely spared and are looking healthy across the country. This means the leaf color should be vibrant and striking instead of muted. From the East to the West coast, get out and enjoy the pretty foliage while you can, and let us know how the leaves look in your area! See our glorious Autumnal Equinox page about the first day of fall, facts, and folklore!
How Does Sunlight Affect Autumn Leaves?
Surprisingly, it is not the weather that is the primary factor that determines when the leaves turn. It’s the amount of sunlight. Leaves manufacture chlorophyll, which stores the energy of the sun. It’s chlorophyll that gives leaves their green color.
When the days grow shorter during fall, less chlorophyll is created. The green fades, and the colors of other leaf chemicals become visible. It’s amazing how pretty these chemicals can be. Anthocyanins make the leaves look red and purple, xanthophyll colors them yellow, and orange leaves contain carotenoids. It’s a rainbow of chemicals.
See the day length in your area.
Weather determines how vivid the fall foliage will be and how long it will last.
How Does the Weather Affect Autumn Leaves?
If the weather is cold enough, it can end the chlorophyll production early. This is why the high mountains in Colorado often have an early leaf season. Cold also makes colors more intense.
At the same time, warm weather can increase production a bit, allowing the green to last longer. In the 120 years of US weather records, temperatures have grown warmer, especially in cities, and the leaves now turn a couple of weeks later than they did a century ago. The US east of the Great Plains and most of the Rockies have been warm.
Temperature departures (°C) over the last 30 days. Source: NOAA/CPC
Dry conditions are rough on trees and actually can end chlorophyll production early, especially for trees that turn red. They may turn red early, but the stress also makes the trees shed their leaves sooner. Dry areas have shorter color seasons.
45% of the continental US is dry.
Fortunately, the drought which affected the 2016 forecast has been eased with precipitation this past year. Given healthy leaf development, we're in for a vivid season this year! Enjoy those autumn colors.