It is that time of the year again when the crisp, cool fall air arrives in the Tennessee Valley and that means that fall color is not far behind. But what causes the leaves to change color and how does the weather play a part in the vibrant display of fall colors?

The science behind the leaves changing color all has to do with chlorophyll. Chlorophyll is how plants trap sunlight and create food. This is what gives leaves their green color during the growing season.

As the seasons change and the sun angle lowers, the intensity of the sunlight decreases. This starts a process in trees and plants as they prepare to go dormant during the winter.

Cells form at the base of the leaf and stop carrying fluids through the rest of the leaf. Sugar then becomes trapped inside the leaf and new color pigments are produced, giving us our different colors before the leaf falls off the tree.

This is how the process works inside of the tree, but did you know that the weather can impact how vibrant this show of colors can be each year? Variables like temperature and rainfall can delay or even mute the fall colors we see.

If the weather has been drier than normal, then we would expect a delayed or muted display in the fall colors. However, if there has been more rainfall, then we can expect leaves to change color on time and be more vibrant.

When it comes to temperatures, warmer temperatures play a negative impact on leaves changing colors. With abnormally warm days, more clouds and warm night colors will be more muted than they would with cooler temperatures. That is seasonally warm days, more sunshine and cool nights lead to more vibrant colors in the leaves.

It will not be long until some color starts to show up in the hills around the Tennesee Valley, be sure to keep watching for color change. In the meantime, check out this map of where leaves are already starting to change.