Many people cite their favorite part of fall as the changing colors of the leaves, but why does this happen? Scientists have studied this very phenomenon and found that three factors influence the changing color of autumn leaves: leaf pigment, length of night and weather, with the most unfailing factor being length of night. As nights grow longer in the fall, a biochemical process in the leaves begins to change the color from green to fall colors like orange and red.
As for the vividness of the colors, we can thank weather conditions (particularly temperature and moisture) that occur before and during the time when the chlorophyll in the leaves is dwindling. A warm, wet spring, favorable summer and warm, sunny fall days with cool nights produce the richest fall colors.
It is fun to think that because of two greatly variable factors that influence the color of leaves alone, no two autumns are ever the same.
Although those of us in Phoenix will not get to experience autumn leaves the same as those on the east coast, we can still appreciate this magical time of year and view the progression of fall colors around the country by visiting the United States Department of Agriculture website.