It’s not everyday that you look up to see a perfect halo shimmering across the sky. The optical phenomenon known as a parhelic circle was spotted over the skies of South Salem, New York, earlier this week, and Facebook fan Ernie LaMadeleine sent us the video.

“The parhelic circle phenomenon happens when millions of ice crystals mirror the sun, forming a circular structure in the sky," said weather.com meteorologist Quincy Vagell. "Typically, only fragments of the circle are visible making the full halo a coveted sight."

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Parhelic circles are generally white in color, often making them difficult to distinguish from clouds, but they can also appear with a bluish or green hue. They always hang in the sky at the same altitude as the sun.

Be sure to look up next time the sun is shining bright on a cloudy day. There’s no telling what you might see.

MORE ON WEATHER.COM: Sun Halos

Duck Key, Fla.

Austin Gruppuso sent this photo of a sun halo from Duck Key, Fla. (Facebook/Austin Gruppuso)