Ask Storm Team 11: What causes fall colors?

Weather

Thursday’s Ask Storm Team 11 question is: “What causes fall colors in the leaves?”

As the days become shorter and the nights become longer, trees begin to show their true colors through chemical processes. 

During the summer, leaves produce chlorophyll, which absorbs sunlight to use as energy. The trees will begin to prepare for winter by blocking off flow to and from the leaf’s stem.  This stops chlorophyll from being replenished and the green color begins to fade.

When the green color fades, the leaf’s true colors begin to show. Carotenoids are a primary pigment that creates yellow from a decrease of chlorophyll. Anthocyanins create red and purple colors as chlorophyll continues to break down. 

How vibrant the colors are depends on the weather. Warm sunny days and cool nights are ideal conditions.

As fronts pass through in the fall into winter, heavy rains and strong winds will speed up the process of leaves falling from the trees and the fall foliage disappears. 

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