Horsetail Fall, located in Yosemite National Park in California, is a seasonal waterfall that flows in the winter and early spring. The fall occurs on the East side of El Capitan. There are a few days every February where this fall is lit up by the setting sun and reflects a bright orange.
Hundreds of spectators gather to witness this event, but the Firefall can be finicky, as several factors must converge to trigger the glowing waterfall.
First, Horsetail Fall must be flowing. If there’s not enough snowpack in February, there will not be enough snowmelt to feed the waterfall, which tumbles 1,570 feet (480 meters) down the east face of El Capitan.
Temperatures must be warm enough during the day to melt the snowpack. If temperatures are too cold, the snow will stay frozen and Horsetail Fall won’t flow.
Second, the western sky must be clear at sunset. If it’s snowing, raining, or even just cloudy, the sun’s rays will be blocked and Horsetail Falls will not light up. Winter weather can be highly variable in Yosemite, however, and days that start off cloudy can clear up by sunset.
If everything comes together and conditions are just right, the Firefall will light up for about ten minutes. To see Horsetail Fall glowing blood red is an almost supernatural experience.