An automatic climate control system for a vehicle determines actual sun load and a virtual sun load based on prescribed virtual heat load data and the external air temperature. A controller is configured to compare the actual sun load to the virtual sun load to obtain an optimized sun load value, and to control the system based on this optimized sun load value. A method for automatically controlling the climate includes determining measured sun load, determining external air temperature, comparing the measured sun load to the virtual sun load based on prescribed virtual heat load data and the external air temperature to obtain an optimized sun load value, and controlling the system based on the optimized sun load value. The virtual sun load and/or the measured sun load are used to determine the optimized sun load value depending on lighting conditions.