A map from 1911 of the climate regions of North America using the classification system developed by Wladimir Koppen, based on the concept that native vegetation is the best expression of climate. The major groups are (A) tropical/megathermal climates, (B) dry (arid and semiarid) climates, (C) temperate/mesothermal climates, (D) continental/microthermal climates, and (E) polar climates. On this map, the major groups are further broken down as (A1) Liana, (A2) Baobab, (B1) Garva, (B2) Simoon, (B3) Mesquite, (B7) Prairie, (C2) Hickory, (C3) Corn, (C4) Olive, (C5) Heath, (C7) High Savanna, (D1) Oak, (D2) Birch, and (E1) Arctic Fox. Tracts enclosed by broken line have distinct dry seasons, with a rain probability of less than 0.20.