Dozens of people are missing in Oregon alone, state Governor Kate Brown has said, as deadly wildfires continue to sweep through US West Coast states.
Fires have been raging in California, Oregon and Washington for three weeks.
Fanned by winds amid record heat, the blazes have burnt millions of acres, destroyed thousands of homes, and killed at least 25 people.
California's Governor Gavin Newsom said the fires show the debate around climate change is "over".
"Just come to the state of California. Observe it with your own eyes," he told reporters from a charred mountainside.
The fires have burnt a total 4.5m acres – an area larger than Connecticut and slightly smaller than Wales – in recent weeks, according to the National Interagency Fire Center.
The smoke pollution from the wildfires has left Oregon's largest city, Portland, with the worst air quality in the world, followed by San Francisco and Seattle, according to IQAir.com.
White House spokesman Judd Deere announced in a tweet on Saturday that President Donald Trump would visit California on Monday.
What is happening in Oregon and Washington?
In Oregon, where firefighters are battling 16 large blazes, 40,000 people are under mandatory evacuation orders.
Oregon's Office of Emergency Management (OEM) says the fires have killed six people, but officials warn the final death toll could be much higher.
Governor Kate Brown on Friday implored householders to stay out of the fire zones despite reports of looting.
"Let me assure you that we have the Oregon National Guard and Oregon State Police monitoring the situation and preventing looting," she said.
Beatriz Gomez Bolanos, 41, told Reuters news agency of her family's frightening drive to safety through fires burning on both sides of their car. She told her four children to close their eyes as they made their escape.
"Everything is gone. We have to start again from nothing, but we are alive," she told the news agency.
At least one blaze in Oregon – the Almeda Fire, one of the most destructive in the state – is being treated as suspected arson.
In Washington State, firefighters are tackling 15 large fires. A one-year-old boy died earlier this week as his family tried to escape a blaze. His parents remain in critical condition.
While natural factors such as strong winds have helped the spread of these massive fires, the underlying heating of the climate from human activities is making these conflagrations bigger and more explosive.
Nine of the world's 10 warmest years on record have occurred since 2005, and the UN warned this week that the five years from 2016 until this year will very likely be the hottest such period yet recorded. Both Oregon and California have warmed by more than 1C since 1900.
The sustained warmth has seen six of the 20 largest fires on record in California all occur this year. In Oregon, the spate of fires has burned nearly twice the average annual losses in just the past week.
In California, a prolonged drought over the past decade has killed millions of trees, turning them into potent fuel for the fires. Mountain regions that are normally cooler and wetter have dried out more rapidly in the summer, adding to the potential fuel load.
Climate scientists had forecast that western wildfires would grow in size, scale and impact – but their predictions are coming to fruition faster than expected.
What is the latest in California?
Governor Newsom, a Democrat, spoke on Friday as he inspected damage from the North Complex Fire, near Oroville in Northern California.
"The debate is over, around climate change," Mr Newsom told reporters. "This is a climate damn emergency. This is real and it's happening."
He acknowledged failings in forest management in recent decades, but added: "That's one point, but it's not the point."
Highlighting the states effort to combat climate change, he said the record heat waves and unprecedented fires were the sort of problems long forecast by scientists.