Nice looking rainbow huh?! Well, nice it is, rainbow it's not. This one is known in the weather world as a circumhorizontal arc, which caused by plate-shaped ice crystals floating in the air. This particular rare sight was caught on film last June 3 of this year at the northern part of Idaho, near the Washington State border.

But to let it become visible the sun has to be very high in the sky. Only at sun elevations of 57.8° (90 -32.2°) or more it shows up as a colourful line along the horizon on the same side of the sky where the sun is. With the sun the circumhorizontal arc also gets higher and at a sun elevation of 67.9° it reaches its maximum intensity. The hexagonal ice crystals that make up cirrus clouds must be shaped like thick plates with their faces parallel to the ground.

This particular occurrence of a circumhorizontal arc in Idaho panned several hundred square miles of sky and lasted for about an hour, according to the London Daily Mail.