While winter in Yosemite National Park offers a spectacular opportunity to witness the national park's unparalleled beauty, there's one phenomenon in particular that draws a crowd.

During the last two weeks of February, the angle of the setting sun transforms the 2,130-foot Horsetail Falls over El Capitan into what many have nicknamed "The Yosemite Firefall." The effect is so convincing that it almost appears as if lava is pouring out of the granite cliffside. For photographers, this spectacle is not to be missed, with many snatching up the best spots to catch the phenomenon as early as 5 a.m. each morning.

The sad news is, the sight has become too popular, drawing crowds that are damaging the area. After the 2019 event, park rangers said enough was enough.

Visitors spilled onto riverbanks, increasing erosion and trampling vegetation. As riverbanks filled, visitors moved into the Merced River, trampling sensitive vegetation and exposing themself to unsafe conditions. Some undeveloped areas became littered with trash, and the lack of restrooms resulted in unsanitary conditions.

The National Park Service is closing access to two of the three prime viewing spots from Feb. 14-27 during key times and is limiting parking in many areas. What that means for eager photographers and nature lovers is a 1.5-mile hike or more.

It's a conflict that has been brewing for years.

"The zeitgeist of it all, the social media, the viral nature of this year's photography played a huge role in (the crowds)," Bay Area photographer Sean Flansbaum told the SFGate in 2016. "I wouldn't say it was out of control, but it became really kinda fevered. It spread like a wildfire, in terms of the popularity."

Firefall can be fickle

Like any other weather-dependent event, the enthusiasm over the natural phenomenon can quickly lead to disappointment when the setting sun is stymied by storms, clouds or fog. Some years, the firefall has failed to show at all during the critical two-week window. And temperature plays a role, too; the temperature must be warm enough for the water to flow. If temperatures are too cold, the snow will stay frozen, as the Yosemite Falls site explains.

The best viewing times for 2020 will be at sunset on Feb. 12 through Feb. 28, with the peak day projected to be Feb. 22. If the show is on, visitors will have about 10 minutes to capture as many photos as possible (or just revel in the fantastic beauty of it all) before the setting sun disappears. For those of us who would rather enjoy the spectacle from afar, check out the video above, which also explains some of the history of the falls and the phenomenon.

Editor's note: This story has been updated since it was first published in February 2017.

Michael d'Estries ( @michaeldestries ) covers science, technology, art, and the beautiful, unusual corners of our incredible world.

Yosemite's 'firefall' has become too popular
The rare and stunningly beautiful phenomenon of Yosemite's firefall at Horsetail Falls only occurs during a two-week window in February.