Each year around this time, the speculation begins. Just how brilliant will the leaves be in the fall? Much weight is given to the weather conditions during the summer months, but there are many other deciding factors.

Why do leaves change?

Underneath that armor of green, the leaves maintain their colors year-round. It's the chlorophyll that is produced during the summer months that mask the brilliant colors until the time is just right.

Come autumn,  shorter days and cooler temperatures cause trees to switch into energy-storage mode. At this time, leaves stop producing chlorophyll, and the green begins to fade away, revealing the original colors beneath.

It's these "anthocyanins," red and purple, and the "carotenoids," yellow and oranges that are on display.

What triggers the changes?

The changes in the leaves are triggered by several factors, one of those being the cooler weather, but the biggest being the length of day.

As the days get shorter and shorter, certain things begin to occur. Animals start gathering their winter food, birds and butterflies start migrating south, and the leaves realize their days are limited and begin slowing down the production of chlorophyll.

How weather impacts the autumn colors

There's only one thing that's  certain. The leaves are going to change colors and fall to the ground. What's uncertain is just how fast those changes will occur, and how brilliant will they be.

PRECIPITATION: A wet spring and summer is better than a dry summer. This means trees are healthy and will retain their leaves during the change.

HARD FREEZE: Cool temperatures, particularly at night, combined with abundant sunlight, promote the formation of more anthocyanins. Freezing conditions destroy the machinery responsible for manufacturing anthocyanins, so early frost means an early end to colorful foliage. A hard freeze while leaves are still green will transition the leaf straight to brown, rather than allowing multiple colors to come out. 

WINDS: High winds will knock leaves off trees early.

September Forecast

So far the Climate Prediction Center is forecasting near average temperatures during September, but above average rainfall. Again these are general predictions. So far, the first two weeks of the month appear sunny and dry with near average highs through the middle of the month.

Fall foliage peak times for 2013

POSTED: 04:37 AM EST Dec 24, 2013    UPDATED: 01:50 PM EDT Sep 05, 2013 

Find out when the leaves will peak in your area and how weather plays a role in the fall colors.

How weather impacts fall foliage
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