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Rare ‘fire rainbow’ puts on colorful show in sky over California national park

A rare weather event known as a fire rainbow was spotted in the sky this week over Pinnacles National Park in central California just east of the Salinas Valley.

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The colorful phenomenon, called a circumhorizontal arc, is caused when light passes through high-altitude cirrus clouds, refracting off the ice crystals in the clouds, according to National Geographic.

National Weather Service meteorologist Roger Gass told SFGate that’s when “you get pretty colors.”

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"It's an optical illusion,” Gass said, and only happens when the sun is very high in the sky.

A runner spotted the surreal sight and sent photos of  the National Weather Service.

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Fire rainbows are similar to another weather event known as iridescent clouds or rainbow clouds that are sometimes visible after thunderstorms above cumulus clouds.

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