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SCIENCE BEHIND: Why do the leaves change colors in the fall?

It's more than the cooler temperatures that make an impact on the fall foliage. The bright colors are a chemical reaction to meteorological elements.

NORFOLK, Va. — Usually, when people think of the changing seasons, they think that cooler temperatures cause varying leaf colors. But cooler temps aren't the only factor in the fall foliage phenomena.

The bright colors that signal the cooler months are a chemical reaction to meteorological elements. So, yes the cooler temps are a factor but most when it comes to the intensity of the colors—warmer temperatures in the fall dim the colors of the leaves.

There's also rainfall—like a drought or a deluge. That moisture, in conjunction with the temperatures year-to-year, brings different vibrant variations each autumn.

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As for when the peak foliage occurs ... that depends on the decreasing daylight. Our days have been getting shorter since the summer solstice back in June and continue to decrease in length until the first day of winter.

Lower amounts of sunlight knock over that first domino in the chemical chain reaction. Since we know when the days start to truly feel shorter, it's the varying temperatures and moisture levels that allow the annual show to take shape.


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