To grasp the effect of nonuniform temperature field, the effects of a nonuniform sunshine temperature field on a large, all-movable radio telescope were analyzed in this study. Based on the overall parameters of a radio telescope model, first, several specific steps of the ray-casting algorithm were introduced for calculating sunlight shadows on radio telescopes, and then a special program was developed for simulating sunlight and shadows on radio telescopes. Second, the periodic air temperature, heat radiation, and heat conduction were computed every half hour under a cloudless sky on a summer day, i.e., the worst-case climate conditions. The transient structural temperatures were then analyzed over a period of several days of sunshine with a rational initial structural-temperature distribution until the whole set of structural temperatures converged to the results obtained the day before. As a result, the temporal and spatial characteristics of the temperature distribution for the radio telescope were statistically investigated. Furthermore, the phenomenon called the solar cooker effect was found to exist in such a Cassegrain reflector system. The variations in the solar cooker effect over time and its spatial distributions in the secondary reflector were observed to elucidate the mechanism of the effect. The results presented here provide some references for the future operation, sensor distribution, and local temperature control of radio telescopes.