Brazil's most intense rainfall is found around the mouth of the Amazon River near the city of Belém, and also in the vast upper regions of Amazonia where more than 2,000 millimetres (78 inches) of rain falls every year. Another important region of heavy rainfall is along the edge of the great escarpment in the state of São Paulo. Most of Brazil, however, has moderate rainfall of between 1,000 to 1,500 millimetres (39 to 59 inches) a year, with most of the rain falling in the summer, between December and April. The winters tend to be dry.

The driest part of the country is the northeast, the so-called "polygon of drought", encompassing 10 percent of the country's territory. In this region rainfall is undependable and the evaporation rate is very high, making it difficult to raise crops. Along the coastline, south from Recife, the mountains trigger rainfall from the Trade Winds. In some places behind the mountains, such as the region south of Salvador, the hinterland is dry because the rain is dumped on the mountains leaving very little for the area behind.