Sun rays

Anti-crespuscular rays formed Tuesday in the setting sun seen from the south end of Edisto Beach. Provided by Trevor Gibbs

It's that radiant crown of sunbeams in the dawn or twilight, a solar spectacle that leaves onlookers in awe: crepuscular rays.

This time of year, the rays can spread across the sky anywhere along the South Carolina coast.

"It could have something to do with the angle of the sun this time of the summer in respect to what is left of clouding inland along the residual sea breeze front at dusk," said Charleston-based meteorologist Shea Gibson with the forecasting company WeatherFlow.

Crepuscular rays appear when the atmosphere holds enough dust or haze to literally scatter sunlight into yellows or reds while clouds break it up into beams, according to a posting by the Department of Atmospheric Sciences at the University of Illinois at Urbana-Champaign. Rays on one side of the sky that stretch the shadow across to the other horizon are known as anti-crepuscular rays, Gibson said.

The rays are actually parallel but appear to converge to the sun because of the viewer's perspective, much like parallel railroad tracks appear to converge as they get farther away, the posting noted.

"I saw these faint rays, and as the sun got closer to the horizon they got brighter," said Trevor Gibbs, a College of Charleston meteorology student who spotted the phenomenon Tuesday off Edisto Beach. "It was mesmerizing."

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Science and environment reporter. Author of Washing Our Hands in the Clouds.