Fire Rainbow

Fire Rainbow Image

This is an image of a Fire Rainbow or Circumhorizontal Arc, which is one of the rarest naturally occurring atmospheric Phenomena. This image was taken at the Idaho/Washington border on June 3, 2006. The entire event lasted about an hour. In order for this phenomena to occur, the clouds must be cirrus at an altitude of 20,000 feet. The clouds have to contain the right amount of ice crystals and the the sun has to hit the clouds at exactly 58 degrees or higher above the horizon.

Cirrus clouds are made up of hexagonal plate crystals. Sunlight entering on the vertical side of the crystal and leaving through the bottom faces, is refracted and separates into a range of visible colours. If the plate crystals are aligned well, they will display a brilliant rainbow of colours.


This page was created August 28, 2006 and updated on April 8, 2007.