Circular rainbow surrounds the sun in Saginaw, Michigan

© Sandie Thompson via Facebook

Several viewers have posted photos on our Facebook wall of what looks like a circular rainbow surrounding the sun.

It's called a "halo" and is caused by cirrus clouds, which are the thin, wispy looking ones around 20,000 feet or higher in the atmosphere.

They typically occur ahead of a storm, like the one approaching us from over the central plains.

Millions of ice crystals within the cloud both reflect and refract sunlight at a specific angle to your eye, which causes the cool looking circular rainbow.

© wnem.com