What is a circular rainbow? Is that really a thing?

Before the clamor of Monday’s storms barreled through South Florida, there was a moment of serenity in Palm Beach Gardens when a rainbow encircled the sun.

The halo of faint colors is an atmospheric phenomenon that happens when when light refracts off ice crystals in a wispy veil of cirrus clouds drifting 20,000 feet above Earth.

Refraction, in the case of sun halos, is the change in light direction because of a change in its speed, according to the National Weather Service. It is most commonly seen when a wave of light passes from one medium to another at any angle other than 90 degrees or 0 degrees.

While usually seen as a bright white ring, what Palm Beach Gardens resident Leonard Walas captured when he looked skyward Monday had the subdued colors of a rainbow - a rare treat before the thunder bellowed.

“I thought it was so unusual and beautiful,” Walas said.

According to EarthSky.org, scientists call the rings “22-degree halos” because the ring has a radius of about 22 degrees around the sun. Halos can also appear around the moon.

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Translucent cirrus clouds and their ice crystals have to be perfectly positioned with respect to the viewer for the halo to appear.

“That’s why, like rainbows, halos around the sun or moon are personal,” and EarthSky.org column notes. “Everyone sees their own particular halo, made by their own particular ice crystals, which are different form the ice crystals making the halo for the person standing right next to you.”