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Millions of people from across the world visit Yosemite National Park each year for an opportunity to take in the sweeping vistas at one of America’s most treasured natural preserves. But hundreds of visitors were ordered to evacuate the park Wednesday as firefighters struggled to contain the encroaching 38,000-acre Ferguson Fire, which has roared for nearly two weeks and remains just 25 percent contained.

Dry conditions have made it difficult for firefighters to contain the flames.

“The conditions are incredibly strenuous, and we’re seeing triple-digit temperatures in places,” said Dan McKeague, a spokesman for the U.S. Forest Service. “Some sections are extremely remote. Access is limited because there aren’t a ton of existing roads.”

Daniel Swain, a climate scientist at U.C.L.A., said that long-term drying caused by rising global temperatures has exacerbated the risk of wildfires in the western United States.

“Over decades there has been a trend toward less moisture in the soil and forest, and that is affecting how dry the vegetation is becoming in summer,” he said.