What Are Sundogs? How Do Sundogs Differ From Rainbows?

While a rainbow is perhaps a familiar term to most people, sundogs - their closely-related weather partners - are not. So what exactly are sundogs?

Here is a brief description of what a sundog is:

When visible, sundogs are always seen horizontally just to the right or left of the sun. They look like a shiny, iridescent patch of cloud, about the size of the sun. In fact they're sometimes called mock suns because the real sun may be hidden behind a cloud. When sunlight, which is made up of all the colors of the spectrum, hits the ice crystals in the cloud, it bends a little. The ice crystal acts as a prism, separating the sunlight into different colors and forming a sundog. Rainbows are basically the same type of thing, except that in rainbows it is raindrops that serve as prisms instead of ice crystals.

So what is the difference between the two besides composition?  Mainly, Sundogs are visible while you are facing and looking towards the sun while rainbows occur in just the opposite location. In addition, rainbows primarily occur only during warmer months like spring or summer while sundogs are visible all year long;  In fact, winter brings a greater chance for encountering sundogs.

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