Environment Planet Earth What Makes This Waterfall Light Up Like Fire? By Jaymi Heimbuch Writer California Polytechnic State University, San Luis Obispo Jaymi Heimbuch is a writer and photographer specializing in wildlife conservation. She is the author of The Ethiopian Wolf: Hope at the Edge of Extinction. our editorial process Twitter Twitter Jaymi Heimbuch Updated January 30, 2020 Horsetail falls lights up at sunset during a certain time each year. Engel Ching/Shutterstock Share Twitter Pinterest Email Environment Weather Outdoors Conservation Horsetail Falls in Yosemite Valley was made famous by photographer Galen Rowell, who was lucky enough to photograph a strange phenomenon that happens only when all the right elements come together. During a two-week window in the spring, the sun sets at just the right angle that it makes the waterfall light up in vibrant orange. It looks like a lava flow streaming down the granite peak. Rowell's photograph of the glowing waterfall at the moment it lights up turned the precisely timed event into a must-see attraction for thousands of people every year. Three things come in to play to make Horsetail Fall glow. The winter has to be wet enough that water is flowing over the fall, which doesn't always happen. The sun has to be setting at the right angle, which only happens two weeks out of the year. And the weather has to cooperate, with few clouds and no fog to obscure the light as it hits the side of the peak. If all of these things align, it's magical. However, it doesn't happen every year. Some people have been visiting the falls during the February window for a decade or more, and have only witnessed it maybe a couple times. It is extremely rare, but worth the wait. This gorgeous video details how the waterfall glows, the photographers who have made it famous, and the effect it has on the people who witness the rare and exceedingly special phenomenon.