CLIMATE IN 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 74°F and an average January high temperature of 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 20 to 26 inches 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 10 to 22 inches 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 70 and 80°F during the year. Annual rainfall, which generally ranges between 60 and 80 inches, 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 Yucatán 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 Yucatán Peninsula, is rainy and tropical. The climate in this region is generally hot and humid, with annual average temperatures of more than 75°F. Maximum precipitation occurs in summer, with average annual rainfall exceeding 80 inch in some areas.

Mexicans have become increasingly aware of environmental issues, ranging from water pollution to the potential side effects of nuclear power. The development of border industries along the northern frontier with the United States has drawn attention to these issues, as these industries have contributed heavily to numerous forms of pollution that have adversely affected both sides of the border. Groups in many border communities, as well as local governments in both countries, have worked together to improve environmental conditions, particularly those related to toxic waste disposal and water pollution.

In central Mexico, the most pronounced environmental problems are the dumping of toxins into local rivers and air pollution, especially in the capital city. Air pollution is exacerbated by the natural setting of Mexico City, which lies in a basin surrounded by mountains. Unless it rains or sufficient breezes occur, airborne particles create a heavy smog on most days. Mexico City has the world’s highest levels of dangerous air pollutants. The government has tried to reduce pollution by controlling industrial emissions and limiting the number of automobiles that can be driven daily. Mexican citizens, unsatisfied with the pace and level of government efforts, have organized grassroots environmental groups. Some have begun to support political candidates at the national level who run on green, or environmentally friendly, campaigns. Domestic and international conservation groups are working in Mexico to create biological preserves, such as the Montes Azulas Biosphere Reserve in the Lacandón rain forest on the border with Guatemala..