Rare Rainbow over Idaho.

A rare, beautiful rainbow (called a circumhorizontal arc) was spotted over Idaho:

Over the fields of northern Idaho, a rare and beautiful sight could be seen. Known as a circumhorizontal arc, it forms as sunlight is refracted through hexagonal ice crystals in cirrus clouds several kilometres above the ground. Sunlight enters a near-vertical face of each crystal and leaves from a horizontal face at the bottom. "Effectively the crystals act as a 90-degree prism for the passing rays," says Evelyn Hesse of the light-scattering group at the University of Hertfordshire in Hatfield, UK.

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