'Firefall': Yosemite's Spectacular Fiery Waterfalls Explained

Waterfalls can be spectacular but there are countless all around the world. There's only one natural Firefall ever discovered -- a glowing golden stream gushing over the side of a jagged cliff -- and it's in Yosemite National Park in California.

The waterfalls is actually Horsetail Falls that flows down the east side of the El Capitan rock formation. When the conditions are perfect, visitors can get a glimpse of the fiery spectacle when Firefall glows supernaturally orange and red during sunset.

Firefall usually occurs mid-February, when the setting sun hits the waterfall at exactly the right angle and the light reflects on the falls, making the water appear golden -- almost like lava.

It's not a sure thing though as a couple of factors are necessary for the waterfall to glow. If Horsetail Falls isn't flowing -- if there's not enough snowpack or the temperature isn't warm enough to melt the snow -- Firefall won't occur. Cloudy days will also block the sun's rays and keep it from illuminating the falls.

Tourists flock to Yosemite National Park in hopes of seeing this unique phenomenon. Lucky visitors who are there when the conditions line up will get to experience Firefall for about 10 minutes before it dims again.

The sunset Firefall is elusive enough as it is, but even more rare is the moonlit Firefall. As astrophotographer Rogelio Bernal Andreo explained in a report from Petapixel, there's only a few nights in a year when it's possible to see it and some years none at all. The moon should not only be in the right place during "moonset", but also bright enough.

"Since the fall usually dries mid-late spring or early summer at best, anytime after June is probably wishful thinking," he wrote in the article. "June itself is a stretch."

Andreo was able to capture a stunning moonlit Firefall against a backdrop of a starry sky on May 9.