The climate varies according to altitude and rainfall. The tropical and subtropical zone (tierra caliente), ranging from sea level to about 900 m (3,000 ft), consists of the coastal plains, the Yucatán Peninsula, and the lower areas of southern Mexico. These areas have a mean temperature of 25–27° C (77–81° F ), with a minimum of 16° C (61° F ) and a maximum of almost 49° C (120° F ). The temperate zone (tierra templada), at elevations of 900 to 1,800 m (3,000–6,000 ft), has a temperate-to-warm climate and a mean temperature of 21° C (70° F ). Mexico City and most other important population centers are in the cool zone (tierra fría), starting at about 1,800 m (6,000 ft), with a mean annual temperature of 17° C (63°F). The highest mountain peaks are always covered with snow.
Most of Mexico is deficient in rainfall, but two coastal belts covering about 12% of the total area—from Tampico south along the Gulf of Mexico and from the state of Colima south along the Pacific—receive an average of from 99 to 300 cm (39–118 in) per year. Annual rainfall may exceed 500 cm (200 in) in Tabasco and Chiapas, while in parts of Baja California, virtually no rain falls. Precipitation is adequate in central Mexico except at altitudes above 1,800 m (6,000 ft), while the northern states are semidesert or desert. Most of the country receives its heaviest rainfall during the summer months.