Humid and warm, the region has all the typical attributes of a tropical environment. Temperatures usually average 27.9 °C during the dry season, and 25.8 °C during the rainy season. Relative humidity is quite high at an average of 88% in the rainy season and 77% in the dry season.

The climate of the Amazon River basin is equatorial, characterized by consistently hot, humid, and wet conditions throughout the year. Because the river is situated so close to the Equator, it does not experience traditional four seasons; instead, the temperature remains relatively stable at an average of 25°C to 28°C (77°F to 82°F). Rainfall is torrential and frequent, with the basin receiving between 1,500 mm and 3,000 mm of rain annually. There are two primary phases: the "wet season" (September to May) and the "less wet" or "dry" season (June to August). Even in the dry season, humidity remains high, averaging 77%, and brief afternoon downpours are still common. The massive rainforest canopy plays a crucial role in this climate, as nearly half of the rainfall is generated by the forest itself through evapotranspiration. This "cycling" of water ensures that the air stays saturated with moisture, creating a greenhouse effect that sustains the incredible biodiversity found along the river’s 6,400-kilometer path.