Firefighters made progress against a ferocious wildfire in the foothills of the Sierra Nevada that forced thousands of residents from their homes in the gateway to Yosemite national park.

The Oak fire started on Friday near the town of Midpines, California, and exploded in size over the weekend.

Burning through dense and dry vegetation on the region’s steep and rugged hillsides, the blaze was fanned by gusty winds and temperatures that hovered around 90F (32C). The extreme nature of the fire meant it turned tall trees into matchsticks and sent billowing black smoke curling over the quaint historic downtown of Mariposa.

But weather conditions improved on Sunday night, and by Monday morning, a heavily resourced firefighting effort achieved 10% containment.

Since Friday, the blaze has consumed more than 16,700 acres. More than 3,000 people were under evacuation orders.

More than 2,000 first responders from state and federal agencies were battling the blaze, attacking it both from the ground and the air. At least 10 homes and other structures had been destroyed, with thousands remaining at risk in its path.

“The growth of this fire is pretty amazing given the fact of how quickly we had resources here,” said Chief Mike van Loben Sels of the Madera Merced Mariposa unit of California’s fire and forestry protection (CalFire). He noted that embers and spot fires were igniting more than a mile ahead of the blaze. “We really threw everything at this thing from the beginning,” he said.

The fire is one of dozens burning across the American west as the region braces for peak fire-risk months that still lie ahead. More than 5.5m acres have already burned in the US this year, roughly 70% more than the 10-year average.

An air tanker drops retardant to try to stop the Oak fire reaching Lushmeadows. Photograph: Noah Berger/AP
© Provided by The GuardianAn air tanker drops retardant to try to stop the Oak fire reaching Lushmeadows. Photograph: Noah Berger/AP

California, a state that in recent years has faced intensifying threats from behemoth blazes, had seen a lighter-than-normal start to its highest-risk season. Spring rains offered a reprieve, delaying the onset of what officials still fear will be another devastating fire year. The Oak fire has showcased how quickly things can change.

On Sunday the California governor, Gavin Newsom, declared a state of emergency for the area, allowing for the deployment of thousands of emergency personnel.


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The cause of the fire remains under investigation.

Firefighters working in steep terrain on the ground protected homes Sunday as air tankers dropped retardant on 50ft (15-meter) flames racing along ridgetops east of the tiny community of Jerseydale. Personnel faced tough conditions that included steep terrain, sweltering temperatures and low humidity, Cal Fire said.

Light winds blew embers ahead into tree branches “and because it’s so dry, it’s easy for the spot fires to get established and that’s what fuels the growth”, said a Cal Fire spokesperson, Natasha Fouts.

Smoke drifted about 200 miles (322km) north toward Lake Tahoe and the same distance west into the San Francisco Bay Area, pollution control officials said.

“Hazy skies may be visible and the smell of smoke is possible at high elevations,” the Bay Area Air District said on Twitter.

Thousands remained under evacuation, awaiting word for when they could return home. Miles away from the flames, fire crews and officers had prepared for the fire’s spread, marking mailboxes with descriptive pages that could aid in the firefight.

The forms include information on if there’s access for large fire trucks, if occupants had vacated the area, whether the property posed any extra risks with visible hazards like propane tanks or overhead power lines, and if a water source was available for use.

In the chaos, a local man named Ron, who declined to share his last name, left behind his medication and his dog Duke, an ageing labrador mix with a bad hip.

“When he was left behind I couldn’t get anybody to help,” Ron said, adding that he had suffered a stroke and still gets disoriented. “But that’s my baby, man.”

CalFire officers Shayon Ascarie and David Janssen came to Ron’s aid, rushing the man back to his evacuated hillside home as the fire crept closer. Helicopters zigzagged overhead and planes dropped fire retardant on the slopes above as the firefighters helped Ron wrangle the terrified Duke into the back of their pickup and grab his pill boxes, before they ferried the duo back down the mountain to safety.

Jessen and Ascarie, who hail from different parts of California but were assigned as partners for the incident, spent the rest of the morning traversing through the towns to post the latest maps and answer questions for a public hungry for information. Along with supplying essential intel, big-incident firefights also often require rescues like Duke’s. “It is part of the job, you are just in the right place at the right time,” Jessen said, adding: “I have a feeling this isn’t going to be the last one.”

Throughout the town of Mariposa, people huddled around their A-frame information posts sharing stories and offering their thanks for the ongoing firefighting effort. Flags flapped overhead, turning what might have otherwise been a breezy reprieve on a hot summer’s day into another foreboding sign that the fire loomed close.

Further up the highway, a roadside diner called Steve’s Sportsman’s Café had become a de facto hub for locals, both those displaced by the fire and others watching and waiting. Outside, a motorcyclist shared videos of his harrowing close call with the fire. It spared his home but claimed his shed, where priceless keepsakes – his grandfather’s fishing poles and guns – had been housed. “Still, it could have been a lot worse,” he said, shaking his head as he walked into the restaurant.

From behind the cash register, Tracy Heidseck dished details on how power outages caused by the blaze did their own kind of damage. “We already lost all our food in our fridge and our freezers,” she said, adding that her well had also run dry and there wasn’t even water to flush toilets. This was one part of fire threats, which she said loom large year after year, that takes a toll. “I am just exhausted,” she said. “I have no water and no power.”

But the community – and the restaurant – have come together during this trying time. Steve Knauf, who owns the diner, ambled over to offer his support. “There’s been a lot of hugs and tears the last couple of days,” he said, adding: “But, it is like one big family in here.”

The Associated Press contributed to this report