Although 90 percent of the country is within the tropical zone, the climate of Brazil varies considerably from the mostly tropical North (the equator traverses the mouth of the Amazon) to temperate zones below the Tropic of Capricorn (23°27' S latitude), which crosses the country at the latitude of the city of São Paulo. Brazil has five climatic regions--equatorial, tropical, semiarid, highland tropical, and subtropical.

Temperatures along the equator are high, averaging above 25°C, but not reaching the summer extremes of up to 40°C in the temperate zones. There is little seasonal variation near the equator, although at times it can get cool enough for wearing a jacket, especially in the rain. At the country's other extreme, there are frosts south of the Tropic of Capricorn during the winter (June-August), and in some years there is snow in the mountainous areas, such as Rio Grande do Sul and Santa Catarina. Temperatures in the cities of São Paulo, Belo Horizonte, and Brasília are moderate (usually between 15°C and 30°C), despite their relatively low latitude, because of their elevation of approximately 1,000 meters. Rio de Janeiro, Recife, and Salvador on the coast have warm climates, with average temperatures ranging from 23°C to 27°C, but enjoy constant trade winds. The southern cities of Porto Alegre and Curitiba have a subtropical climate similar to that in parts of the United States and Europe, and temperatures can fall below freezing in winter.

Precipitation levels vary widely. Most of Brazil has moderate rainfall of between 1,000 and 1,500 millimeters a year, with most of the rain falling in the summer (between December and April) south of the Equator. The Amazon region is notoriously humid, with rainfall generally more than 2,000 millimeters per year and reaching as high as 3,000 millimeters in parts of the western Amazon and near Belém. It is less widely known that, despite high annual precipitation, the Amazon rain forest has a three- to five-month dry season, the timing of which varies according to location north or south of the equator.

High and relatively regular levels of precipitation in the Amazon contrast sharply with the dryness of the semiarid Northeast, where rainfall is scarce and there are severe droughts in cycles averaging seven years. The Northeast is the driest part of the country. The region also constitutes the hottest part of Brazil, where during the dry season between May and November, temperatures of more than 38°C have been recorded. However, the sertão , a region of semidesert vegetation used primarily for low-density ranching, turns green when there is rain. Most of the Center-West has 1,500 to 2,000 millimeters of rain per year, with a pronounced dry season in the middle of the year, while the South and most of the Atlantic coast as far north as Salvador, Bahia, in the Northeast, have similar amounts of rainfall without a distinct dry season.

Data as of 1997