Rare ‘ghost rainbow’ rises from mountains in Texas national park. What causes it?

A rare phenomenon was seen spanning across the sky in a Texas national park Thursday morning.

But what causes it?

Guadalupe Mountains National Park shared a photo of a beautiful fogbow, which is sometimes called a ghost rainbow or white rainbow, reaching between cliffs in the Far West Texas desert.

Similar to colorful rainbows, fogbows form when sunlight is refracted by water droplets, according to the park. But the droplets in a fogbow are “super tiny,” which makes the colors too faint to spot.

“It is also a reminder of the arctic air that is on the way this weekend,” the national park posted on Facebook.

Fogbows are sometimes considered a weather phenomena of the arctic, where “microscopic ice crystals are suspended in the air, changing how light and sound travel over distances” and forming unique sights in the sky, according to the National Snow & Ice Data Center.

An arctic blast has “entrenched” much of the central U.S., and it is forecast to continue bringing winter weather to much of the country into next week, according to the National Weather Service.