Hazy skies over Chicago are due to smoke from West Coast wildfires.
Washington Governor Jay Inslee called the crisis a "a blowtorch over our states" in an interview with ABC on Sunday.
Los Angeles Mayor Eric Garcetti accused Trump of perpetuating a lie that only forest management can curtail the massive fires seen in recent years.
"He fails to protect us from the pandemic, from an economic free fall, from racial unrest, from the ravages of climate change", Biden said, before parroting one of the president's signature lines of attack: "It's clear that we're not safe in Donald Trump's America".
What's the latest on the ground?
In California, almost 16,500 firefighters are grappling with 28 major wildfires, according to the California Department of Forestry and Fire Protection, or Cal Fire.
They warned that the strong southerly winds and low humidity forecast for Monday could bring an elevated fire risk, and potentially have an impact on the North Complex Fire, which has scorched 106,000 hectares and is only 26% contained.
"The 16 large fires in OR total about 878,000 acres of fire, while the 13 large fires in Washington are at about 676,000 acres", according to the Bureau of Land Management office for those two states.
At least 10 people have been killed in OR in the past week.
What are the politicians saying?
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"If we have four more years of Trump's climate denial, how many suburbs will be burned in wildfires?" he asked.
"This is truly the bellwether for climate change on the West Coast".
Governor Newsom called the crisis a "climate damn emergency" and condemned "ideological BS" plaguing the debate. Trump continues his campaign rallies in front of thousands of sign-waving supporters, few of whom wear face masks.
For his part, Trump focused Monday on forest management and the role of what he described as "exploding trees", further exasperating scientists and state officials.
The manifold effects of rising global temperatures require "leadership, not scapegoating", Biden said, and they demand that the president "meet the threshold duty of the office: To care. This isn't about forest management or raking". Auto and truck emissions are the single biggest contributor to climate change, and California has always been empowered to set its own rules.
The ominous prediction, which came as historic wildfires scorch much of the country's West Coast, sounded like a prophecy out of the Book of Revelation.
Nine of the world's 10 warmest years on record have occurred since 2005, and the United Nations warned this week that the five years from 2016 until this year will very likely be the hottest such period yet recorded.
All told in California, almost 17,000 firefighters were battling 29 major wildfires on Sunday, state fire authority Cal Fire said.
Crews in Jackson County, Ore., were hoping to venture into rural areas where the Alameda Fire has abated slightly with slowing winds, sending up thick plumes of smoke as the embers burned.
Have you been affected by the USA wildfires? Mountain regions that are normally cooler and wetter have dried out more rapidly in the summer, adding to the potential fuel load.
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