Come to Yosemite in February and you may be shoulder-to-shoulder with photographers hoping to get a shot of Horsetail Fall in the evening. When conditions are right, rays of the setting sun align with the falling water to set the cascade ablaze with light—a natural display called the ‘firefall.’ And in a bit of added mystique, Horsetail Fall itself is an ephemeral waterfall—it flows only for a short time in the winter and early spring.