Spectacularly Fiery Optical Illusion Makes Its Annual Return to Yosemite

It's "Firefall" season.

After witnessing Yosemite’s epic “Firefall,” you’d be forgiven for wondering whether there’s a secret volcano hidden somewhere in the national park. During the spectacular display, thin ribbons of fiery gold and tangerine cascade off El Capitan’s 3,000-foot rock wall — a stark contrast to the rush of clear water that typically spouts out of Horsetail Fall. But in February, both Horsetail Fall and the Firefall are one and the same because of very specific circumstances.

The Firefall is currently on display at Yosemite, although park rangers warn that it might not make it past the weekend. In mid-February, for a maximum of 10 days per year, the Firefall appears for about 10 minutes around sunset. During that time, park visitors hike a mile to the recommended viewpoint, hoping to catch a glimpse and — if they’re lucky — a dazzling shot of what appears to be flames streaming down the rock face.

This spectacular shot was shared on Tuesday. 

But the Firefall is just an optical illusion requiring three key ingredients: water, a perfect sunset, and perfect weather conditions. According to the National Park Service, “this unique lighting effect happens only on evenings with a clear sky when the waterfall is flowing.” It warns that “even some haze or minor cloudiness can greatly diminish or eliminate the effect.”

That’s because the Firefall appears when the light of the sunset perfectly hits the waterfall, which itself has to have a steady flow. That’s not always guaranteed because sometimes there’s not enough snow and rain in the Sierra Mountains to fuel it. Your best shot at seeing it is to sit through the entire sunset, right as it begins at 5:42 pm PST. That way, you won’t miss the moment when the sun hits Horsetail Fall just right.

This picture was uploaded Tuesday. 

This phenomenon is reminiscent of a human-made Firefall that historically occurred at Glacier Point, another popular Yosemite destination. That now-retired tradition began accidentally in 1872, when smoldering embers from the Glacier Point Mountain House Hotel were kicked over the edge of the cliff at the evening’s end. People watching from the valley below enjoyed the site, so it turned into a tourist attraction. In 1968, however, the nightly Firefall ended; officials had decided national parks should be natural, and pouring embers off a cliff didn’t really fit with that. Luckily for modern viewers, you can see the real natural thing in February, if only for two short weeks.