A sun halo (sometimes called sundog) shined bright around the sun Monday afternoon. This was actually due to moisture streaming in from tropical depression Cristobal which brought us all the rain Tuesday morning.
These halos, which in some cases look like rainbows around the sun are formed when light from the sun shines through clouds that are made of ice crystals. When you get way high up in the atmosphere, air temperature typically drops below freezing after a certain point. What we saw Monday afternoon was moisture being spread out from Cristobal which had frozen into millions of tiny ice crystals.
Much like a glass prism, when sunlight travels through these ice crystals, the light is refracted and spread outward. The refraction process also causes sunlight to be split into all the other colors of the light spectrum (this is because white light is actually just all colors we can see-- combined!).
The product is the neat, perfectly circular rainbow which goes all the way around the sun.
Sun halo photos from viewers
Special thanks to Kim, Denise W., Pam S. and Missy R. for the photos!