Surya Siddhanta
अत्यासन्नतया तेन ग्रीष्मे तीव्रकरा रवेः। देवभागे सुराणाम् तु हेमन्ते मन्दतान्यथा॥
Hence, owing to his exceeding nearness, the rays of the gun are hot in the hemisphere of the gods in summer, but in that of the demons in winter : in the contrary season, they are sluggish.
english translation