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.I saw the same thing last tuesday!
June 19, 2006—It looks like a rainbow that's been set on fire, but this phenomenon is as cold as ice.Known in the weather world as a circumhorizontal arc, this rare sight was caught on film on June 3 as it hung over northern Idaho near the Washington State border (map of Idaho).The arc isn't a rainbow in the traditional sense—it is caused by light passing through wispy, high-altitude cirrus clouds. The sight occurs only when the sun is very high in the sky (more than 58° above the horizon). What's more, the hexagonal ice crystals that make up cirrus clouds must be shaped like thick plates with their faces parallel to the ground.When light enters through a vertical side face of such an ice crystal and leaves from the bottom face, it refracts, or bends, in the same way that light passes through a prism. If a cirrus's crystals are aligned just right, the whole cloud lights up in a spectrum of colors.This particular arc spanned several hundred square miles of sky and lasted for about an hour, according to the London Daily Mail.