The amount and brilliance of autumn colors are related to weather conditions before and during the time chlorophyll in the leaves is dwindling. Temperature and moisture are the main influences.

The most spectacular color displays occur after a series of warm, sunny days and cool, crisp but not freezing nights. During the sunny days, leaves produce lots of sugars which are sealed in by the cool nights. These conditions — lots of sugar and lots of light — spur production of the brilliant anthocyanin pigments, which tint reds, purples, and crimson. Because carotenoids are always present in leaves, the yellow and gold colors remain fairly constant from year to year.

The amount of moisture in the soil also affects autumn colors. Like the weather, soil moisture varies greatly from year to year, so no two autumns can be exactly alike. A late spring, or a severe summer drought, can delay the onset of fall color by a few weeks. A warm period during fall will also lower the intensity of autumn colors. A warm wet spring, favorable summer weather, and warm sunny fall days with cool nights produce the most brilliant autumn colors.