Saturday January 20, 2018

Rare "Rainbow" Spotted Over Idaho (photo)
  Posted by: Digg on Jun 20th, 2006 9:29 AM
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). The hexagonal ice crystals that make up cirrus clouds must be shaped like thick plates with their faces parallel to the ground.

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