Why do leaves change color?

By Dave Williams

CHARLESTON, S.C. (WCIV) - As summer fades to fall, leaves start to change color from their bright green.{} The green hue in leaves is due to chlorophyll.{} That is the substance in plants which absorbs sunlight needed for food production.

The process is called photosynthesis.{} Plants and trees extract carbon dioxide from the air, mix it with water and the sun's energy to make oxygen and glucose, a sugary substance used to grow and survive.

What happens in the fall is the hours of daylight fade and nights become cooler.{} The green chlorophyll senses these changes and exits the leaves back into the tree until spring.{} There is not enough sun in the winter for plants to grow.{} The reds and yellows in the leaves have always been there, they have just been dominated by the green.

This is how and why leaves change color.

Now for an examination of the Lowcountry's weather through the end of November.

As the days grow shorter, the summer's heat begins to abate.{} Keep in mind water cools off more slowly than land and air, so hurricane season continues to the end of November.

At the beginning of September, the average high is 88, and by the end of the month it is back to 81, lows go from 71 back to 63.{} October's numbers are 81 dropping to 74, and the lows are 62 back to 52.{} Finally November's average highs go from73 to 66 at the end, and lows are 51 to 44.

Rain numbers are a little more easier to look at, cooler air holds less moisture.{} So, September averages 6.10 inches, October, 3.75 inches and November is 2.43 inches.

Most of the summer has been a touch on the cool side, until the end of August and beginning of September when thing heated up.{} As far as the fall 2013 outlook goes, the Climate Prediction Center has equal chances of temperatures being above, or below average, and also equal chances of rain being above or below average.

Take that forecast literally, and the rest of the fall overall should be pretty close to the averages.{} For foliage viewing, it is typically better in parts of the Upstate and especially higher in elevation in the Appalachian Mountains.{} Many leaves in the Lowcountry remain on the trees year round and do not change color.