Sun dogs are bright spots sometimes seen to the left or right of the Sun. They form when sunlight is refracted through flat, hexagonal ice crystals suspended in the atmosphere, often in high, thin clouds. They are related to halos but are not reflections from a second Sun.
Ice crystals bend sunlight
As sunlight enters and exits plate-like ice crystals, it changes direction. When many crystals are oriented with their flat faces roughly horizontal, they send concentrated light toward observers at particular angles. The common pair of bright spots appears about 22 degrees from the Sun, near the distance of a 22-degree halo. [1]
Why sun dogs can have color
Refraction bends wavelengths by slightly different amounts. A sun dog may show red on the side closest to the Sun and cooler colors farther away, although it can look mostly white. Sun dogs are also called parhelia or mock suns. Their appearance depends on the Sun’s height and the ice crystals’ orientation. [2]
How to observe one safely
Never stare at the Sun. Block the solar disk with a building or tree trunk and look to either side. A sun dog is an atmospheric optical effect, not a second object. Related displays include lunar halos and rainbow-colored clouds.
Frequently asked questions
Frequently asked questions
Are sun dogs the same as a halo?
They are related effects caused by ice crystals. A halo is a ring; sun dogs are bright patches usually seen on either side.
Do sun dogs predict cold weather?
They indicate ice crystals are present, often in high clouds, but are not a reliable forecast by themselves.
Can they appear at sunset?
Yes, and they can be especially noticeable when the Sun is low. Never look directly at the solar disk.
Sources and evidence
- National Weather Service — Halos, Sundogs and Sun Pillars ↗
Explains refraction by ice crystals and the appearance of sun dogs.
- U.S. Geological Survey — Rainbows, Water and Light ↗
Describes parhelia and ice crystals in the atmosphere.
- NOAA Photo Library — Parhelion ↗
Provides an observed example of a sun dog.
Sources consulted: 2026-10-18. Written with AI assistance and checked against the linked references; not independently reviewed by a subject specialist. Sources do not endorse this article. See our editorial policy.
Revision: Initial editorial draft prepared 18 October 2026; claims are tied to linked sources and retain stated limitations.