SAN FRANCISCO (NYTIMES) - Across a hellish landscape of smoke and ash, authorities in Oregon, California and Washington state battled to contain mega-wildfires Sunday (Sept 13) as shifting winds threatened to accelerate blazes that have burned an unimaginable swath of land across the West.

The arrival of the stronger winds Sunday tested the resolve of fire crews already exhausted by weeks of combating blazes that have consumed around 2 million hectares of desiccated forests, incinerated numerous communities and created what in many places was measured as the worst air quality on the planet.

"There's just so much fire," said Ryan Walbrun, a fire weather meteorologist with the National Weather Service.

"And so much smoke."

The fires, which have killed at least 24 people in the last week alone, have engulfed the region in anguish and fear, as fairgrounds have turned into refugee camps for many who have been forced from their homes.

The choking smoke cast a dark pall over the skies and created a vision of climate-change disaster that made worst-case scenarios for the future a terrifying reality for the present.

"I drove 600 miles up and down the state, and I never escaped the smoke," Democratic Oregon Senator Jeff Merkley said Sunday on the television programme This Week.

"We have thousands of people who have lost their homes. I could have never envisioned this."

As the West burns there is consensus among scientists of the role that climate change is playing in the size and intensity of the fires.

"Fundamentally the science is very, very simple," said Philip B Duffy, a climate scientist who is president of the Woodwell Climate Research Centre.

"Warmer and drier conditions create drier fuel," said Duffy, a physicist.

"What would have been a fire easily extinguished now just grows very quickly and becomes out of control."

Winds are often the decisive factor between fires that can be controlled and those that move with such ferocity and speed that the best authorities can do is move people out of the way.

Walbrun of the National Weather Service said that winds generated from a slow-moving storm system off the coast of Oregon were expected to last most of the week and to blow at 24-50kph. The winds could have the beneficial effect of clearing some of the toxic smoke haze hovering in the atmosphere from Los Angeles to Seattle.

But for firefighters, the shift in winds represents a 180-degree change in direction in many areas, threatening their progress in containing the fires.

The National Weather Service issued a "red flag warning" because of the prospect of windy and dry weather in southern Oregon and nearby counties in California.

In California, which has experienced catastrophic fires every year since the wine country north of San Francisco was devastated in 2017, the fires are encroaching on many of the same areas previously burned, adding new trauma.

The town of Paradise, where more than 80 people died in a 2018 firestorm and most structures were destroyed, is on the edge of one of the largest fires now raging in the state.

In Oregon, blazes are reaching into areas untouched by fire for decades.

"We haven't had anything ever this close," said Margot Cooper, who for the last three decades has lived in Scio, Oregon, a farming and logging town southeast of the state capital, Salem.

"It's the first time it's literally in our backyard."

Last week a 13-year-old boy was killed in a nearby canyon, apparently as he attempted to drive his grandmother to safety.

In nearby Gates, Oregon, refugees from the fires were exhausted after five days of living in dingy motels or cars, eating donated pizzas for dinner and, all the while, not knowing whether their homes had burned down or were standing.

Police cruisers blocked traffic along a highway heading into the mountains east of Salem, where the Beachie Creek fire was still burning out of control.

Some families were able to pass through.

Other convoys of pickup trucks threaded their way onto side roads and skimmed the edges of farm fields in search of alternate routes.

Some were seeking needed medications, others lost pets and signs of break-ins.

"Everything's still on fire," said Mike Alexander, 29, who has been coming and going since Monday night, when the wildfire surged up the hillside behind his home.

Some evacuation warnings eased Sunday in areas just south of Portland.

But many towns remained unreachable.

Law enforcement officials set up a hotline Sunday for people in the incinerated lakeside resort towns of Detroit and neighbouring Idanha to have deputies check on their homes.

For days, fire crews in Aumsville, a little town outside Salem that was untouched by the fire, have been heading into the mountains to help other firefighters try to get a handle on the 188,000-acre Beachie Creek fire.

Firefighters have been running on adrenaline, sleeping in a donated trailer that was dropped in their parking lot, then heading back up into the fire.

"People are prepared, but not for a fire of this magnitude," said Aumsville's fire chief, Roy Hari.

Most of what has burned in the West has been in remote forests but in Oregon, entire communities along I-5, the main north-south interstate highway along the West Coast, have been razed.

An ongoing concern in California is the number of dead trees in the Sierra Nevada forests, where a number of the largest blazes are burning.

The US Forest Service has counted 163 million trees killed, mostly as a consequence of a prolonged drought that ended in 2017.

President Donald Trump is scheduled to visit McClellan Park, California, on Monday to be briefed on the wildfires.

After weeks of silence on the fires, Trump acknowledged their severity Saturday.

"I spoke to the folks in Oregon, Washington," he said.

"They've never had anything like this."

In Gates, where dozens of homes burned, Darren Richardson, 55, and his neighbours have become an improvised fire brigade.

They filled up rain barrels, kiddie pools and small tanks at a nearby fire station and patrolled their streets and backyards to douse around property lines and try to put out fires burning in tree stumps.

"I'm not leaving," Richardson said this weekend, dressed in camouflage and holding a shotgun in his right hand, as he stood outside his home.

"I watched the whole town burn down."