The north area of Brazil embraces a great part of the Amazon Basin, representing the largest extension of hot and humid forest on the planet. The area is cut, of an end to the other, by Ecuador and is characterized by low altitudes (0 to 200 m/0 to 656 ft). There are four main systems of atmospheric circulation that act in the area, they are: system of winds of Northeast (NE) to East (E) of the Atlantic South and Azores, subtropical anticyclones, generally stable in nature; system of winds of West (W) of the mass equatorial continental (mEc); system of winds of North (N) of the Convergence Intertropical (CIT); and system of winds of South (S) of the Polar anticyclone. These last three systems are responsible for variability of the climate and for the rains in the area. With regard to temperatures, the climate is hot, with annual medium temperatures ranging from
24 to 26 °C (75.2 to 78.8 °F).
Regarding the pluviosity, there is not a homogeneity as it occur with the temperature. In the mouth of the river Amazonas, in the coast of Pará and in the western section of the area, the total annual pluviometric index exceeds 3,000 mm (118.1 in) in general. In the direction NO-SE, of Roraima to east of Pará there is less rain, with annual totals in the order of 1,500 to 1,700 mm (59.1 to 66.9 in).
The rainy period of the area occurs in summer & autumn, the exception being Roraima and of the north part of Amazonas, where the maximum pluviometric indexes occurs in winter, due to influence of the climatic conditions of the Northern Hemisphere.