Monthly outgoing long wave radiation (OLR), sea surface temperature (SST), and rainfall in central-eastern South America were used to identify the rainfall characteristics of the South American Monsoon system (SAMS). The rainfall climatology for the area allowed the identification of two seasons with marked precipitation regimes: a well defined rainy season in December, January and February, and a dry season in June, July and August. The period where the summer monsoon in South America is more intense was identified from September-February, and this can hold up to 80% of the annual total rainfall. The onset of the rainy season as estimated from outgoing long wave radiation pentad climatology showed that on the northeastern part of the monsoon area, rainy seasons are shorter as compared to the rest of the region. The correlation analysis between sea surface temperature anomalies and rainfall in the monsoon area, represented by the Summer Monsoon Rainfall Index (IMV), show that both Atlantic and Pacific affect the variability of rainfall on the region. In the Pacific, 3 areas that may exert some influence on the IMV were identified. This influence can be related to an atmospheric-oceanic coupling, that favors the propagation of Rossby waves that affect the South Atlantic Convergence Zone and possibly the monsoon rainfall variability. On the Atlantic, the band of negative SST-rainfall correlations between 5 degrees S and 20 degrees S can be explained through the intensification of the winds related to these SST anomalies, which entails a stronger moisture transport into the continent and thus an increment of rains on this area.