A model for temperature effects in p-a junction solar cells is introduced. The temperature of solar cells and the losses in the solar cell junction region caused by elevated temperatures are discussed. The model developed is examined for low-cost silicon solar cells. Flats of output power and efficiency as functions of the time throughout the day are presented. In order to improve the shape of the output power and efficiency curves throughout the day the coherence between technical parameters of the solar cells and the climate in the operation region is observed and examined. It is shown how the drop in output power around noon can be avoided by fitting technical parameters of the solar cells to the climate.