Sun dogs, also known as parhelia, are bright spots that appear on either side of the sun, often creating a halo effect. They occur when sunlight refracts through ice crystals in the atmosphere, typically found in cirrus or cirrostratus clouds. This phenomenon is most commonly seen in cold weather conditions. Sun dogs are usually visible when the sun is low on the horizon, often during sunrise or sunset. They can appear as two bright spots, sometimes accompanied by a halo around the sun. The presence of sun dogs indicates the presence of ice crystals high in the atmosphere.