We studied the interannual variability of the beginning, end and duration of South American monsoon system (SAMS) for the period 1956–2006. The mean beginning date was 10 October, whereas the mean end date was 6 April, and the mean duration was 174 days. The beginning of SAMS showed a tendency to start earlier and the end date showed a tendency to delay; thus, the duration of SAMS showed a tendency to increase by about 7 days in 10 years. We found that the beginning and end dates of SAMS have significant positive correlation with sea surface temperature (SST) of an earlier period at southwest Africa in the South Atlantic Ocean. This suggests the potential of SST in the prediction of the beginning and end dates of SAMS.