Weather Words: Sun Halo

Chances are, you have seen a sun halo, but there’s a possibility you just didn’t know the name for it. If you’ve ever noticed a bright, circular ring around the sun, that’s a sun halo.

These halos are created when sunlight interacts with ice crystals high in the atmosphere, usually in cirrus or cirrostratus clouds. As light passes through and reflects off these tiny ice crystals, it bends (or refracts) at a specific angle, usually 22°, producing a ring that can surround the sun or moon. The effect not only casts a beautiful, often rainbow colored ring, but also a subtle signal of the sky’s icy, high-altitude clouds.

Sun halos can vary in brightness and color depending on the size and orientation of the ice crystals. Sometimes the ring appears bright white, while other times, faint red on the inside and blue on the outside can be seen. Halo phenomena are often a hint that weather patterns are changing, as the high clouds that create them can precede frontal systems or storms.

Jennifer Gray is a weather and climate writer for weather.com. She has been covering some of the world's biggest weather and climate stories for the last two decades.