Mexico’s topographic diversity and latitude range provide it with a variety of climatic conditions, which usually occur over short distances. More than half of the country is south of the Tropic of Cancer. In these areas, from May to August, tropical ocean air masses from the Gulf of Mexico, the Caribbean Sea and the Pacific are attracted by relatively low pressure on land and are the main source of precipitation. Tropical hurricanes generated in the oceans on both sides of the country are common in coastal lowland areas from August to October. The climate of northern Mexico is located at the latitude of one of the largest desert regions in the world. It is strongly affected by the semi-permanent Pacific subtropical anticyclone, which minimizes precipitation.
In the tropics, the temperature change is small in each season, and the temperature change between the warmest and coldest months is usually only 10°F (5°C). In these areas, winter is defined as a rainy rather than a cold season. Since altitude rather than latitude is the main climate influence in southern Mexico, several vertical climate zones can be identified. In tropical Mexico, from sea level to over 3,000 feet, there is a tierra caliente (“hot soil”) with uniform high temperature. For example, the average daily temperature in Veracruz in the Gulf of Mexico is about 25°C (77°F). The templada layer (“temperate land”) extends to approximately 6,000 feet. Jalapa is located above 4,600 feet above sea level and has an average daily temperature of 66°F (19°C). Tieling (“Cold Land”) extends to 11,000 feet. Pachuca is located below 8,000 feet and has an average annual temperature of 59°F (15°C). Above the strata are Palamos or alpine pastures, while in central Mexico, the stratigraphic helada (“frozen ground”) or permanent snow line lies between 13,000 and 14,000 feet.
To the north of the tropics, the temperature range increases significantly, with the largest in the northern central part of Mesa del Norte. In the northern inland areas, the temperature in summer and winter is mostly extreme. The country’s highest temperature exceeds 110°F (43°C), occurring in Baja California, California, and the northern Sonoran and Chihuahua deserts in July and August, respectively. In the high mountains of northern Mexico and the central and northern regions of North Mesa del Norte, the lowest temperature is usually no lower than 32°F (0°C).
Most areas of Mexico lack sufficient precipitation for at least a certain period of the year. Except for the highlands, all areas north of the Tropic of Cancer usually receive less than 20 inches (500 mm) of rainfall per year and are classified as tropical deserts or savanna in climate. Almost Baja California, most of Sonora and most of Chihuahua receive less than 10 inches of annual rainfall. Most areas of central and southern Mexico receive less than 40 inches of annual rainfall, mainly from May to August, and are classified as savanna or plateau savanna climates. Only the Gulf Coast Plain and nearby mountains receive a lot of rainfall throughout the year. Combined with a uniform high temperature, a tropical rainforest climate is created in the area.