Why our autumn weather has been nearly perfect for brilliant fall colors

Paulo Falco

SEATTLE -- I've heard from more than a few that this year's fall color displays has been among the better ones witnessed in recent years.

Turns out, they're probably right, as the overall weather of the past several weeks has been conducive to a longer, brighter autumn leaves display.

Temperature, sunlight, and soil moisture greatly influence the quality of the fall foliage display, according to the U.S. National Arboretum. As the nights get longer, the process to transport nutrients and minerals from the roots to the leaves breaks down --- causing the leaves to lose their green color.

Since the process depends on amount of daylight, the autumn leaves begin to turn roughly the same time of the year no matter what the weather has been. But the weather can influence how long the season lasts.

"A growing season with ample moisture that is followed by a rather dry, cool, sunny autumn that is marked by warm days and cool but frostless nights provides the best weather conditions for development of the brightest fall colors," the arboretum says.

MORE | The Science of Color in Autumn Leaves

Freezing weather destroys a secondary process that allows leaves' natural orange/red colors to come through, making for an early end to the season. Rainy/windy weather obviously will knock the leaves off the trees quicker. A dry summer can also weaken the stems connecting the leaves to the trees, making it easier for the leaves to fall off sooner or be knocked off in rain and/or wind.

But so far, this autumn has been plentiful in the warm, sunny day/cool nights tally, hasn't had a freeze, and has only had one real windy day take aim at the trees. Through the 29th, Seattle is having about a spot-on normal October for temperatures -- both highs and lows -- with only six days of rain that would probably be considered heavy enough to make a dent in tree canopies. So while coming off our ultra dry summer have probably made the leaves easier to knock off had it been an extendedly-stormy October, the relative calm has mitigated that effect.

Thus even as we head into November, which is usually well past the peak of the season, there is still plenty of color to be enjoyed! And with sunny, calm, dry weather with cool nights predicted to continue for the next few days, conditions remain optimal for viewing autumn leaves!

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