MAINE, Maine — Question: What are "sun dogs" and why are they only visible sometimes? Does it have to do with moisture in the air?
Sun dogs and halos are occasionally seen in our sky. These optical phenomena both are related to sunlight and ice crystals from thin clouds.
Sun dogs are colored spots of light, usually seen when the sun is low on the horizon in the winter. They're left, right or both of the sun, and occur as the sunlight is refracted or bent by ice crystals.
Sun halos are seen a little more frequently here and can occur year-round. Similarly, the halo forms as the sunlight refracts off the ice crystals in high, thin cirrus clouds. Very often they'll happen ahead of a storm, as the cirrus clouds responsible for their formation occur in those situations.