Most of the vast and scenic valley in the heart of California’s Yosemite National Park will close to visitors this weekend in an unusual closure triggered by forecast flooding from rapid snowmelt.

The closure will begin at 10 p.m. Friday and last through at least Wednesday, May 3, possibly longer, depending on how quickly snow melts from the mountains toward the Merced River through Yosemite Valley, he said Tuesday. the National Park Service.

The agency said that accommodation and camping reservations will be automatically canceled and refunded.

The closure of an area famous for iconic landmarks like the towering granite formations of El Capitan and Half Dome comes as central California braces for a looming heat wave, with highs in the 90s and overnight lows. well above freezing point.

The heat wave is expected to accelerate spring thaw after record winter snowfall in parts of the Sierra Nevada mountain range. Strong runoff down the mountain slopes could cause already swollen rivers to overflow their banks.

Daniel Swain, a climate scientist at the University of California, Los Angeles, said in a YouTube presentation Monday that a «big thaw» had arrived.

State climatologist Michael Anderson said significant flooding was more likely in late May, rather than next week, and reservoir operators are releasing water now to make room for more water later.

Anderson told reporters that he expects any meltwater flooding to be less severe than the deluge that resulted from Pacific storms in March.

One area of ​​concern is a large watershed in the northern San Joaquin Valley along the Tulare River, where a long-dry lake bed has filled in with storm runoff in recent weeks, submerging large tracts of farmland and ranches.

“This climate whiplash is what the climate crisis looks like,” Gov. Gavin Newsom said while visiting the Tulare Basin Tuesday.

About 100 miles to the north, the Merced River at the Pohono Bridge in far west Yosemite Valley is forecast to exceed flood stage by the end of this week, the park service said.

Yosemite’s vast glacial valley received a record 40 inches of snow during the winter, prompting the closure of the entire park to the public on February 25 for three weeks.

That closure marked one of the longest and most expansive weather-related closures at the park, according to park spokeswoman Nancy Phillipe. Established in 1890 and now encompassing more than 759,000 acres in the southeastern Sierras, the park sees about 4 million visitors a year, she said.