Colors most affected by weather are the red tones created by anthocyanin. On warm sunny days lots of sugar is produced in the leaves. Trees exposed to brighter sunlight generate the reaction between the anthocynanins and the excess sugar creating the bright red hue.
Cooler temperatures cause the veins in the leaves to gradually close preventing the sugars from moving out which preserves the red tones. Thus a succession of warm sunny days and cool crisp nights can paint the most spectacular display of color.
The level of moisture in the soil can also affect autumn color. A severe summer drought can delay the onset of color change by weeks. Ideal conditions for producing the most brilliant colors are a warm wet spring, favorable summer weather, and sunny fall days with the cooler temperatures at night.
The genetics of different tree species help determine what color the leaves will turn. Color depends on the levels of iron, magnesium, phosphorous, or sodium in the tree and the acidity of the chemicals in the leaves. Some tree species displaying yellow foliage are ash, birch, beech, elm, hickory, poplar, and aspen.
Red leaves are seen most often in dogwood, sweetgum, sumac, and black tupelo trees. Some oaks and maples present orange leaves while others range in color from red to yellow, depending on the specific species.
Deciduous forests and trees, with their many broad leaves that change color almost in unison, display the most noticeable fall color. Evergreen species also display fall colors, only slowly and gradually. The appearance of autumn color starts as early as mid September in more northern latitudes, and moves southward reaching its peak in October, but color continues to appear in more southern regions and higher elevations in the west throughout November.
Only a few places in the world have the combination of tree species and climatic conditions necessary for the most vivid fall foliage. Some of the best locations with broadleaved deciduous trees and favorable conditions for brilliant fall color are