More than 6,000 people living outside the Yosemite National Park in California have been ordered to evacuate amid a fast-moving wildfire as drought and high temperatures continue to fuel dangerous blazes in the western United States.

Governor Gavin Newsom on Saturday declared a state of emergency in Mariposa County as the Oak fire, which began a day earlier, spread over 4,800 hectares (11,900 acres).

That came as firefighters were making progress on a separate blaze – the Washburn fire – inside Yosemite that had threatened a grove of cherished ancient giant sequoia trees.

The Oak fire was the largest so far this year in the state, and comes amid a particularly active wildfire season, which scientists say has become increasingly more destructive over the last 30 years due to climate change.

More than 400 firefighters were battling the latest California fire, using helicopters, other aircraft and bulldozers to bring the flames under control.

It described the Oak fire’s activity as “extreme with frequent runs, spot fires and group torching”.

By Saturday morning, the blaze had consumed 10 residential and commercial structures, damaged five others and was threatening 2,000 more structures, Cal Fire said.

The blaze prompted numerous road closures.

A plane drops retardant while battling the Oak Fire in Mariposa County, California

“The fire is moving quickly. This fire was throwing embers out in front of itself for up to 2 miles [3km] yesterday,” said Daniel Patterson, a spokesman for the Sierra National Forest.

“These are exceptional fire conditions,” he said.

The cause of the fire was under investigation.

Firefighters work to keep the Oak fire from reaching a home in Mariposa County, California

“Explosive fire behavior is challenging firefighters,” Cal Fire, the state fire agency, said in a statement Saturday.

There have been a total of 37,774 wildfires in the US this year, covering about 2.24 million hectares (5.5 million acres), the highest number in both categories since 2012, according to the National Interagency Fire Center.

As of Saturday, there were 95 active fires, covering about 913,400 hectares (2.26 million acres) in 15 US states.

Last week, the centre also warned of extreme conditions for three blazes in Texas and one in Wyoming.There have been a total of 37,774 wildfires in the US this year, covering about 2.24 million hectares (5.5 million acres), the highest number in both categories since 2012, according to the National Interagency Fire Center.

As of Saturday, there were 95 active fires, covering about 913,400 hectares (2.26 million acres) in 15 US states.

Last week, the centre also warned of extreme conditions for three blazes in Texas and one in Wyoming.