The Appalachian Mountains were a boreal forest (Jack Pine and Spruce)
during the last ice age, all the way south to Atlanta,
2 million to ~10,000 years ago. It was not only cooler during this time,
but dry. As the weather warmed, it also got wetter and
key to the dominance of hardwoods, the rainfall is
uniform throughout the year. Conifers are better adapted
to dry conditions as experienced on the west coast, while
the Angiosperms (hardwoods) are better in shady conditions.
Rainfall in this area is from 40 to 90 inches per year.