Picturesque ‘Fire Rainbow’ Appears Over South Carolina

posted: 08/19/15
by: Danny Clemens
Circumhorizontal arc in Portugal
nbarr via Wikimedia Commons

South Carolinians had quite a surprise earlier this week, when a strange, rainbow-like cloud was painted across the sky over Isle of Palms:

Without clarity. So beautiful

A photo posted by Carole Rich Williams (@icrw70) on

The striking phenomenon is colloquially referred to as a fire rainbow, although it has nothing to do with fire and isn't technically a rainbow.

Scientifically known as a circumhorizontal arc, the optical phenomenon occurs when sunlight refracts through plate-shaped ice crystals, according to weather.com. The Sun must also be at least 58 degrees above the horizon in order for the fire rainbow to be visible.

"To produce the rainbow colors, the sun's rays must enter the ice crystals at a precise angle to give the prism effect of the color spectrum," meteorologist Justin Lock told local news station WYFF. "Again, it has to do with getting the precise angle."

Becuase such a specific angle is necessary for the fire rainbow to be visible, the phenomenon is most common at middle latitudes.

Learn more about weather:

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Cloud Seeding

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