Solar radiation has a direct effect on plant growth and, thus, is required for many simulation models of crop growth and productivity, and evapotranspiration. For locations where measured values are not available along temporal and/or spatial scales, it can be estimated using empirical models. This study was conducted to simulate the solar irradiance from temperature using Richardson model. The effect of seasonality was investigated by subdividing the yearly data into two subsets, wet and dry period. The calibration coefficients are comparable with the values developed elsewhere. The calibrated models were then tested against independent data sets. For the yearly data, the root mean square error (RMSE) was 1.38 MJ/m2/d compared with 1.82 MJ/m2/d for wet period and 1.33 MJ/m2/d for dry period. The percentage error for yearly data was 17 , compared with 26.6 for wet period and 14.5 for dry period. Results showed that the simulation models provide reasonably accurate estimates of irradiance and hence, can be used for non-instrumented periods and at sites away from calibrated site. Seasonal subdivision of the data adds accuracy of estimates.