At least 31 people have died as wildfires continue to rage across the West Coast of the United States.
Authorities are expecting more fatalities, and Oregon’s emergency management director said officials were preparing for a possible “mass fatality event”.
Meanwhile, smoke from the wildfires is posing a health hazard to millions as firefighters battle the deadly blazes which have already obliterated some towns and displaced tens of thousands of people.
More than 40,000 people in Oregon have been evacuated and about 500,000 are in different levels of evacuation zones, having been told to leave or to prepare to do so, Governor Kate Brown said.
This is not an act of God. This has happened because we have changed the climate.Washington governor Jay Inslee
More than 1,500 square miles have burned in Oregon during recent days, nearly double the size of a typical year and an area larger than Rhode Island, authorities said.
In Washington state, the land burned in just the past five days amounted to the state’s second-worst fire season, after 2015, Governor Jay Inslee noted.
“This is not an act of God,” Mr Inslee said. “This has happened because we have changed the climate.”
And in California, 16,000 firefighters were battling 28 major wildfires across the state, although 24 were sparked on Thursday and quickly contained.
In all, 22 people have died in California since wildfires began breaking out across the state in mid-August.
US President Donald Trump will visit California on Monday for a briefing on the West Coast fires, the White House announced.
Democratic presidential candidate Joe Biden and the governors of California, Oregon and Washington state – all Democrats – have said the fires are a consequence of global warming.
“We absolutely must act now to avoid a future defined by an unending barrage of tragedies like the one American families are enduring across the West today,” Mr Biden said.
Smoke created cooler conditions in California and Oregon, but it was also blamed for making the dirtiest air in at least 35 years in some places.
The air quality index reading on Saturday morning in Salem, the Oregon capital, was 512 and the scale normally goes from zero to 500.
“Above 500 is literally off the charts,” said Laura Gleim, a spokesperson for the Oregon Department of Environmental Quality.
Because past air quality was rarely so poor, the government’s yardstick for measuring it capped out at 500, Ms Gleim said. The department started monitoring in 1985.
The weather conditions that led up to the fires and fed the flames were likely a once-in-a-generation event, said Greg Jones, a professor and research climatologist at Linfield University in McMinnville, Oregon.
A large high-pressure area stretching from the desert Southwest to Alaska brought strong winds from the east toward the West Coast, reducing relative humidity to as low as 8% and bringing desert-like conditions, even to the coast, Mr Jones said.
Instead of the offshore flows that the Pacific Northwest normally enjoys, the strong easterly winds pushed fires down the western slopes of the Cascade Range.
It is not clear if global warming caused the conditions, Mr Jones said, but a warmer world can increase the likelihood of extreme events and contribute to their severity.