Interannual warm and cool events in the subtropical/mid-latitude South Indian Ocean region, that are not associated with extreme phases of the El Ni¿o Southern Oscillation, are examined. During these events, there tend to be periods of significantly anomalous rainfall in large parts of southern Africa. Typically, the sea surface temperature (SST) anomalies become significant during the austral autumn of the first calendar year of the event, and dissipate during the spring of the following year. Examination of cloud cover and near-surface winds suggests that atmospheric forcing may contribute towards the SST anomalies, via changes in insolation and wind-driven upper ocean mixing and surface fluxes. ¿ 1999 American Geophysical Union