Flying rivers are “atmospheric watercourses” formed by air masses loaded with water vapor, often accompanied by clouds, and driven by winds.
These invisible air currents pass over our heads, carrying moisture from the Amazon Basin to the Center-West, Southeast and South of Brazil.
This moisture, under favorable weather conditions, such as a cold front coming from the south, for example, turns into rain.
It is this action of transporting enormous amounts of water vapor by air currents that is called flying rivers.
The Amazon rainforest acts as a water pump.
It pulls in moisture evaporated by the Atlantic Ocean and carried by the trade winds to the continent.
As it flows inland, the moisture falls as rain in the forest.

Source: Amazon Agency