Temperate forest regions in East Asia and Europe have commonly been divided into warm-temperate (evergreen), with mild winters, and cool-temperate (deciduous), with cooler summers. In North America, though, there is a large “typical temperate” gap between mild southern winters and cool northern summers. A resulting three-part subdivision works also in East Asia and Europe. This paper summarizes and evaluates accepted and other putative climatic limits of beech and oak forests across North America, including Mexico. In North America, summergreen (deciduous) broad-leaved forest types are delimited northward by wood structure, with diffuse-porous species extending further north than ring-porous species. Against dryness, closed forests generally require at least four consecutive warm-wet months, in order for trees to produce viable fruit. Deciduous trees may extend slightly into the (humid) subtropics, including mountains in Mexico, but deciduous trees may also be replaced by evergreens. Beech occurs where soil is continuously moist but also aerated, as elsewhere, but often mixes with oak and other canopy trees. Oaks generally tolerate both wetter and drier conditions. In Mexico, beech behaves somewhat as it does in mountains of China. Oaks, on the other hand, are quite widespread in Mexico, but climatic limits and data are more elusive.