Circumhorizon arc over Alabama
We receive a lot of great photos from our viewers, including pictures of cool phenomena like the circumhorizon arc sent in to us Tuesday afternoon by Willis Brannon!

The circumhorizon arc looks like an upside down rainbow, but it's formed differently. Rainbows occur when light is refracted by water droplets, usually just after rain. Circumhorizon arcs however are one of many halos that can be formed by light's interaction with ice crystals.

Ice crystals are found high in the sky and can refract light into a variety of halos and shapes depending on where the sun is in the sky relative to the ice crystals and what kind of crystals are present. To form a circumhorizon arc the light is refracted by plate crystals oriented so that the light can enter through the plate's side.

If you spot any cool sights around the Tennessee Valley, share them with us!