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

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."

"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.

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