A brief review is given of the spatial and temporal pattern of sea surface temperature (SST) observations for the southern hemisphere. An analysis is made of 20 years (1950--1969) of observations of mean monthly SST for each degree square along the shipping routes, and relative variability is assessed on seasonal, latitudinal, and geographical bases. Highest variability occurs in oceanic regions of the western boundary currents, of current confluence, of upwelling, and also of convergence of low-level atmospheric flow, notably in the central South Pacific. Within the data limitations the relative areas of above- and below-normal SST are measured for selected tropical ocean regions near Australia for 6 years of extremely high and low extent of annual continental rainfall and for transitions from very dry years to very wet years and vice versa. The 3 extremely dry years are found to occur with an average reduction of some 14% in the area of above-normal SST as compared with the 3 extremely wet years; the corresponding regional seasonal mean atmospheric pressure is above normal in dry years and below normal in wet years. The greatest interannual changes in rainfall extent are also accompanied by corresponding transitions in the area of above-normal SST. Evidence suggests that the extent of above-normal SST over the whole ocean (including higher latitudes) surrounding continental Australia may be closely associated with extreme rainfall years.