Heat of sun and evaporation are related to each other. These are the important phenomenon and the process related to this is water cycle. Sun rays as heat is important for evaporating water. Unless the water will not be evaporated and will be soaked by clouds it will not come down in the form of rain. Little bit sunrays will result in less evaporation and less evaporation will result in less rain which is not good. So in this way heat of sun is related with evaporation as it results in rainfall.