Fall foliage: Why leaves change color

Aspen trees with mountains in background (Getty Images)

DENVER (KDVR) — Fall is a wonderfully colorful time thanks to the changing leaves around us. But why do leaves change color each fall?

Leaves have chlorophyll in them that gives them green pigment during the warmer months. In the fall, when the temperatures get cooler and the sun angle changes, the tree’s chlorophyll starts to break down.

Eventually, the green color disappears and other colors become visible. The leaf color depends on the pigment present in the leaf.

Xanthophyll causes leaves to turn yellow, carotene causes orange leaves, and anthocyanin causes red leaves.

When fall brings drier days with cooler nights, the colors of the leaves appear brighter.


While fall officially began on September 22, leaf peepers in most parts of the United States will have to wait a few weeks until peak foliage time, according to one prediction map.

Great Smoky Mountains National Park is one of the most popular places to catch leaves changing color, and its 2022 Fall Foliage Prediction map is a tool designed to help travelers decide on the best time to visit.

Using a complex algorithm, the map forecasts county-by-county fall foliage based on millions of data points. The data includes historical temperatures, historical precipitation, forecast temperatures from the National Oceanic and Atmospheric Administration, historical leaf peak trends and even user-generated information.

The northernmost states in the contiguous U.S. are the first to see the changing of leaves, and the trend slowly trickles down to the southernmost states.

Across the U.S., the peak foliage happens sometime between Oct. 3 and Nov. 21.

Check out this map to see when fall colors will peak near you.

Izzy Karpinski and Jocelina Joiner contributed to this report.


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