Daily potential surface radiation values were calculated for selected South African weather stations. These were used, together with various air temperature parameters, to derive regression equations to estimate actual surface solar radiation at sites lacking the required instrumentation. A single regression equation for the whole country proved more effective than several region-specific expressions. The equation was assessed at 27 widely-ranging sites which had not been used in the regression analysis. According to Willmott's Index of Agreement (D), solar radiation estimates were best in the winter rainfall region (D≥0.92) but were quite acceptable for the rest of the country (D≥0.78).