NASHVILLE, Tenn. (WKRN) – “Sundogs” are fairly common this time of the year when the sun is low on the horizon. They are caused by cirrus clouds, which are composed of ice crystals that refract the light into “rainbows.”
You usually see two sundogs, one on either side of the sun. They are also called “mock suns” or “parhelia.”
The origin of the word “sundog” is obscure. Some say they are called so because they follow the sun like a dog follows its master.
The ice crystals could cause a “halo” completely around the sun under other circumstances, similar to a ring around the moon. I saw a total halo around the sun in the Tampa Bay area in summer when the sun was overhead.
The difference in the two has to do with the orientation of the ice crystals to the viewer and the sun.