While vegetation has something to do with the climate, the sudden
changes to which we are subject are due to the configuration of the
land. The Rocky Mountains and the Appalachian Range rising at either
edge of the continent form the immense valley through which the
Mississippi takes its course; and these two factors of the high
mountains and the broad plains have the greatest influence on the
climate.
Our immense length of seaboard and the proximity of the Gulf Stream are
also agents for engendering our variable climate.
Trees protect moisture from rapid evaporation, and a wooded country is a
blessing to its inhabitants, defending their dwellings from wind in
mountainous districts.
The denudation of the forests tends to destroy the moisture of the
atmosphere, but has little effect on the sudden transitions from heat to
cold.