This paper reports temperature influence on radiation degradation of hydrogenated amorphous silicon (a-Si : H) solar cells. Degradation behaviors of a-Si : H solar cells irradiated with protons at 331 K are compared with that at 298 K (room temperature). Variations with time in the post-irradiation electrical properties are also investigated. It is found that the radiation degradation of the electrical properties at 331 K is significantly smaller than that at room temperature. Also, all the electrical properties (short-circuit current, open-circuit voltage, output maximum, and fill factor) recover with time after irradiation even at room temperature. The characteristic time of thermal annealing of short-circuit current is larger as the temperature is higher. These results indicate that temperature during irradiation and elapsed time from irradiation to measurement is an important parameter for radiation degradation of a-Si : H solar cells. Therefore, these parameters should be controlled in conducting the ground radiation tests. Copyright © 2012 John Wiley & Sons, Ltd.