Sun sets waterfall ablaze in California's Yosemite National Park 'firefall'

Yosemite National Park, United States: A spectacular "firefall" wowed nature-watchers in California's Yosemite National Park on Wednesday, with the setting sun lighting up a waterfall like a ribbon of fire.

For just a couple of weeks every year the last rays of daylight hit Horsetail Falls, appearing to set the water alight like a river of lava gushing down a mountainside.

The phenomenon, which lasts just a few minutes at sundown and which draws tourists from across the country, relies on a rare combination of perfect conditions.

"When the sun drops at the exact right angle, it reflects upon El Capitan," Yosemite National Park Public Affairs Officer Scott Gediman told AFP.

"It's a combination of the sun reflecting on the water, clear skies, water flowing. If all of that comes together, it's magical."

California, along with much of the western United States, is in the grip of a years-long drought that has badly depleted its rivers.

But bountiful downpours that started the year - causing deadly flooding in some places - have left the state in much better shape and watercourses are flowing.

California's signature blue skies put in an appearance on Wednesday, meaning visitors to Yosemite - who were in exactly the right place at exactly the right time - got their chance to see the firefall.

"The pictures I've seen are just gorgeous," said amateur photographer Terry Cantrell, who had traveled from Fresno. "Everybody wants to have their own, so this is what I'm trying to do."

The long wait and the freezing temperatures were all worth it for fellow picture bug Whitney Clark from San Francisco.

"Based on how the sun sets up against the mountain or the rock, it creates a really good fire effect for photographers and you can get a beautiful picture of it," she said.