Thousands of people have been ordered to flee their homes and businesses near a wildfire burning near Yosemite National Park on Saturday.
The wildfire that started Friday afternoon has now grown to cover more than 26 square kilometers (10 square miles), according to the California Department of Forestry and Fire Protection.
Evacuation orders are now in place for more than 6,000 people living in the sparsely populated rural area.
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“The explosive behavior of the fire is challenging firefighters,” the department said, describing the fire as “extreme with frequent runs, spot fires and group fires.”
The fire had destroyed 10 residential and commercial structures by Saturday morning and was threatening 2,000 more.
It has caused numerous road closures, including Highway 140, which is one of the main routes into Yosemite.
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More than 400 firefighters are battling the blaze in the Sierra Nevada foothills, armed with helicopters and other firefighting aircraft, as well as bulldozers.
The fire has been fueled by heat, low humidity and extremely dry vegetation caused by the worst drought in decades, although its initial cause is unknown.
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Daniel Patterson, a spokesman for the Sierra National Forest, said climate change has made the region much warmer and drier over the past 30 years, causing California to experience increasingly large and deadly wildfires.
Last year, in August, nearly 43,000 Californians were under evacuation orders as a dozen wildfires raged across the state.
“The fire is moving fast. This fire was throwing embers ahead of it for up to two miles yesterday. These are exceptional fire conditions,” Mr Patterson warned.
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Residents have been sharing images on social media of a huge pyrocumulus cloud billowing into the atmosphere.
Andy Bollenbacher, a meteorologist with the U.S. National Weather Service, said the top of the cloud had extended up to 30,000 feet into the sky Friday night.
The risk is that in extreme conditions wildfires can start to create their own weather system when the smoke forms a pyrocumulonimbus cloud, similar to normal cumulonimbus or thunder clouds that produce hail, thunder and lightning.
Under current conditions, this weather, and the accompanying lightning and stronger winds, could spark even more fires in a chain reaction of destruction.