Rare Moonbows to Form Over Yosemite This Weekend

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At Yosemite National Park this weekend, conditions are just right for a rare sight called a moonbow — basically, a lunar rainbow.

One of the first wilderness parks in the United States, Yosemite National Park is a great place to see a moonbow due to the park's spectacular waterfalls. One waterfall, Yosemite Falls, is famous for its rare moonbows.

A moonbow is basically a rainbow that appears as the moon sets, but it only happens a few times each year as light is reflected off the surface of the moon rather than from direct sunlight.

A full moon arrived today (July 15), and according to the U.S. Naval Observatory, the moon will be at an altitude less than 42 degrees through the weekend. That means the moon will be just right to create a moonbow at Yosemite Falls, despite a few clouds in the area, reports AccuWeather.com.

To see a moonbow at Yosemite Falls you need clear skies, enough water in the falls to create sufficient mist, dark skies, and bright moonlight not blocked by the surrounding mountains.

Moonbows usually appear white to the naked eye, because their light is not bright enough to activate cone color receptors in our eyes, optics expert Les Cowley of Atmospheric Optics told AccuWeather. Some lucky viewers have reported colors, however, when the moon has been especially bright, Cowley said.

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