Goodnight moon!There’s an old weather saying: ring around the moon means rain soon. Actually scientists call them halos. There’s truth to the saying, because high cirrus clouds often come before a storm and these clouds contain millions of tiny ice crystals and can result in this halo effect. The halos are caused by both refraction, or splitting of light, and also by reflection, or glints of light from these ice crystals. The crystals have to be oriented and positioned just so with respect to your eye, in order for the halo to appear.