A window of time has just opened in Yosemite National Park when nature photographers wait, as if for an eclipse, until the moment when the sun and earth align to create a fleeting
phenomenon. This marvel of celestial configuration happens in a flash at sunset in mid-February – if the winter weather cooperates.

On those days the setting sun illuminates one of the park’s lesser-known waterfalls so precisely that it resembles molten lava as it flows over the sheer granite face of the imposing El Capitan. Every year growing numbers of photographers converge on the park, their necks craned toward the ephemeral Horsetail Fall, hoping the sky will be clear so they can view the spectacle first recorded in colour in 1973 by the late renowned outdoors photographer Galen Rowell.

“Horsetail is so uniquely situated that I don’t know of any other waterfall on earth that gets that kind of light,” said Michael Frye, who wrote the book The Photographer’s Guide to Yosemite. “How many are perched on a high open cliff? Most are in an alcove or canyon and won’t get the sun setting behind it. Yosemite’s special geography makes this fall distinctive,” he said. “If you hit it at just the right time, it turns this amazing colour of gold or red-orange,” said Frye, a photo instructor with the Ansel Adams Gallery in the park. To be successful in photographing the watery firefall, it takes luck and timing, and the cooperation of nature.

Horsetail Fall drains a small area on the eastern summit of El Capitan and flows only in the winter and spring in years with adequate rain and snow, which is scarce this year. Experts say it doesn’t take a lot of water for the fall to light up. Most importantly, the southwestern horizon must be clear, and February is the time of year when storm clouds often obscure the setting sun.

When conditions come together, the scrawny Horsetail Fall is the shining star of a park famed for its other waterfalls – raging Yosemite Fall and Bridalveil Fall. But Horsetail is the longest free-falling one, with a drop of 450 metres before it hits granite and spills another 150 metres.

The fire lights up around dusk and lasts for about two minutes. The best views are east of El Capitan along the main roads into and out of Yosemite Valley. Most photographers gather at the El Capitan picnic area, a small pullout marked only by a sign with a table etched on it. But park officials say the inexperienced can look for the hordes of tripods and cameras to find a vantage point.

Recent storms and snowfall mean the finicky fall is flowing again, and park officials are hopeful it will last until February 24, which is generally the last day of the year it can be seen.

Once an obscure event, park officials say that internet discussions have made it more popular in recent years.