The Buzz

Hoping for dazzling fall color? Fingers crossed for sunny days and cool nights

Hoping for fall color like this? Fingers crossed for warm, sunny days and cool nights. (Photo courtesy of Tyler Keene)

The verdant green of summer will soon start slipping away, but the vibrancy of the colors that replace that lush green is influenced in part by the weather we are experiencing now. The bottom line: If you love to soak up the fall color, cross your fingers for warm, sunny days and cool but not cold nights.

The combination of warm, sunny days and cool, crisp nights is optimal for dazzling fall color, the National Weather Service reports. Warm days that are cloudy and rainy tend to result in less brightly colored fall leaves. The worst-case scenario for leaf peepers would be an early cold snap, because a hard frost can put an end to fall color before it even really starts, causing the leaves to wither and drop before they change color.

Some of the colors we look forward to each fall have really been in the leaves all along, but the pigments that create these warm fall colors have been masked by chlorophyll, the pigment that makes leaves green, according to the Illinois Department of Natural Resources. When the sun starts to set earlier and earlier and the angle of the sun becomes lower in the sky, trees begin to produce less chlorophyll. As less chlorophyll is produced, it begins to disappear from the leaves, allowing the colors from those other pigments to shine through.

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Different pigments produce different colors. Yellows and oranges are the result of pigments called carotenoids, IDNR reports. Specifically, yellow leaves result from a pigment called xanthophyll, while orange is the result of the pigment carotene. Pigments called anthocyanins are what give us red and purple leaves. Carotenoids have been hiding in the leaves since they first budded out in the spring, but anthocyanins are produced by the trees in the fall in response to excess sugar content and bright light, according to the U.S. Forest Service.

Sunlight can make these yellow, orange, red and purple pigments more vivid because the trees will produce more sugars under sunlight, and those pigments are what result in bright and vivid fall color. For our red and purple leaves, soil conditions also contribute to color. Anthocyanins will look red in acidic soil but purple in alkaline soil, according to IDNR. This is why the same tree type can sometimes produce leaves of different colors if they are growing in different soil conditions.

While the weather today will influence the vividness of fall color, so, too, has the weather we experienced earlier in the summer. Specifically, rainfall during the summer months affects fall color, and not enough rainfall in the summer can push back the annual autumn show or make it shorter and less vivid than usual, according to the U.S. Forest Service. Even a late spring can delay the fall color show by a few weeks.

Once the color display starts, the weather is important to how long it will last. If you want to soak it up for as long as possible, hope for days free of heavy rain and winds. These conditions can put a quick end to fall color by prematurely knocking leaves to the ground. 

Variations in vividness aside, fall's annual leaf change generally looks about the same from year to year as far as the colors go because certain trees produce certain colors of leaves. Aspen and poplar trees have golden yellow leaves, while hickory trees have a golden bronze color and oak leaves can be red or brown, according to the forest service. Beech trees have tan leaves, while dogwoods have purplish leaves. Leaves on maple trees vary by species. Red maples have bright red leaves, while black maples have yellow leaves and sugar maples have orangish-red leaves.

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