Implementing the GOSSYM/COMAX Expert System requires the use of historical and current weather data. Current weather data is easily obtained, but historical data is not always available. To implement GOSSYM/COMAX in Texas, actual temperature and precipitation data were located, but solar radiation data were not available. To obtain the required historical weather files, the WGEN weather generation model was modified to generate solar radiation data that is correlated to the actual weather data already available. The generated solar radiation data were combined with actual temperature and precipitation data to produce historical weather files for Texas.