Donald Trump has again dismissed concerns over climate change, this time as he visited fire-ravaged California.
Fires in California, Oregon and Washington state have burned nearly 5m acres of land and killed dozens of people since August.
The blazes have laid waste to several small towns, destroying thousands of homes.
Mr Trump, a climate change sceptic, blamed the crisis on poor forest management.
California Wildfires: August/September 2020 - In pictures
"It'll start getting cooler, you just watch... I don't think science knows actually,” the president said.
It comes after Democratic presidential candidate Joe Biden called the US leader a “climate arsonist".
He told an event in Delaware that four more years of Mr Trump in the White House would see "more of America ablaze".
The fires have filled the region's air with harmful levels of smoke and soot, bathing skies in eerie tones of orange and sepia while adding to a public health crisis already posed by Covid-19.
Ten deaths have been confirmed during the past week in Oregon, the latest flashpoint in a larger summer outbreak of fires accompanied by catastrophic lightning storms, record-breaking heat waves and bouts of extreme winds.
Those incendiary conditions gave way over the weekend to cooler, moister weather and calmer winds, enabling weary firefighters to gain ground in efforts to outflank blazes that had burned largely unchecked last week.
Fire managers cautioned that the battle was hardly over.
Thunderstorms forecast for later in the week could bring much-needed rain but also more lightning. Officials also braced for a rise in the death toll.
As disaster teams scoured the ruins of dwellings engulfed by flames amid chaotic evacuations last week, Oregon's emergency management authorities said they had yet to account for 22 people reported missing in the fires.
