Land and Resources, Climate
tropic of Cancer, Valley of Mexico, moderate climate, central plateau, southern Mexico
The climate throughout much of Mexico is characterized by high temperatures and moderate to low rainfall. The highland climates vary considerably with elevation, but the central plateau generally has a moderate climate with few extremes of hot or cold. Mexico City, for example, has an average July high temperature of 23°C (74°F) and an average January high temperature of 21°C (70°F). Cities at lower elevations on the plateau have somewhat warmer climates. The northern and central areas of the plateau are arid and semiarid, with the drier regions receiving about 300 mm (about 12 in) of rainfall annually. Rainfall increases in the southern regions of the plateau, which receive about 500 to 650 mm (20 to 26 in) of rainfall annually, with most of it typically falling in the summer. Traditional rainfall patterns in the Valley of Mexico have been altered by substantial industrial pollution, which has become so serious that the rainy and dry seasons no longer follow a regular annual cycle.
Much of northwest Mexico—including Baja California and the northern regions of the Pacific Coast lowlands—is quite arid, receiving less than 130 mm (5 in) of rain per year. The northern Gulf Coast plains are semiarid, receiving about 250 to 560 mm (about 10 to 22 in) of rainfall annually. As on the central plateau, rainfall increases toward the south on both the western and eastern coasts.
The tropic of Cancer, which marks the northern limits of the tropics, passes through the southern tip of Baja California and crosses central Mexico. Much of southern Mexico has a tropical climate with distinct rainy and dry seasons; the Gulf Coast has more regular and abundant rainfall than the southern regions of the Pacific Coast. Temperatures in these coastal regions range between 21 and 27°C (70 and 80°F) during the year. Annual rainfall, which generally ranges between 1,500 and 2,000 mm (60 and 80 in), comes mainly during the rainy season of May to October. Mexico’s Gulf Coast is subject to hurricanes that pass through the region and often cause extensive damage.
The northern Yucatan Peninsula is hot and semiarid. Annual rainfall ranges between 500 and 1,000 mm (20 and 40 in). The extreme southern part of Mexico, including the Chiapas Highlands and the southern regions of the Yucatan Peninsula, is rainy and tropical. The climate in this region is generally hot and humid, with annual average temperatures of more than 24°C (75°F). Maximum precipitation occurs in summer, with average annual rainfall exceeding 2,030 mm (80 in) in some areas.
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