RIngs around the sun are caused by cirrus clouds -- high altitude clouds that form above 30,000 feet. Cirrus clouds form when water droplets condense around tiny mineral particles in the air, then freeze. The clouds appear to form a ring around the sun -- or the moon -- when light reflects off the ice crystals and refracts by passing through them.
Reading the Clouds
Cirrus clouds typically appear in clear weather, but signal distant or approaching storms. This is because the water-and-mineral-laden air that forms these clouds is pushed up into the high reaches of the atmosphere -- where it freezes -- by warm air fronts moving underneath it. Rising warm air causes storms. If you see a ring around the sun, it usually means there's a distant storm forming, which may reach your area in a matter of days.
Beware of Sun Gazing
Halos and other solar and atmospheric events can be beautiful and riveting, but beware. You can sustain permanent retinal damage by looking directly at the sun, even in dim conditions. Never look directly at the sun, even if you can do so comfortably. You can't feel retinal damage and won't experience symptoms until several hours after exposure.