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.
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.