Most of Mexico is above 1000 m (about 3300 ft) in elevation; as a result most of Mexico has a more temperate climate than might be expected given its latitude.
The famous explorer Alexander von Humboldt, one of the founding fathers of physical geography and meteorology, was the first to describe the vertical differentiation of climatic and vegetation zones in Mexico. Writing in 1811, he proposed the terms tierra caliente, tierra templada, and tierra fría, still widely used by non-specialists today.
Tierra caliente (hot land) includes all areas under about 900 m (3000 ft). These areas generally have a mean annual temperature above 25°C (77°F). Their natural vegetation is usually either tropical evergreen or tropical deciduous forest. Farms produce tropical crops such as sugar-cane, cacao and bananas.
Tierra templada (temperate land) is the area between 900 and 1800 m (3000 to 6000 ft) where mean annual temperatures are usually between about 18°C and 25°C (64°F to 77°F). The natural vegetation in these zones is temperate forest, such as oak and pine-oak forest. Farms grow crops such as corn (maize), beans, squash, wheat and coffee.
Tierra fria (cold land) is over 1800 m (6000 ft) where mean annual temperatures are in the range 13°–18°C (55°–64°F). At these altitudes pine and pine-fir forests are common. Farm crops include barley and potatoes. On the highest mountain tops, above the tierra fría is tierra helada, frosty land.
Even higher, and almost permanently under snow and ice, is the tierra nevada, snow-covered land.