The fire that began Monday afternoon has ripped through over 78 square miles.
Authorities say about 5,000 homes have been evacuated and about 600 homes, businesses and other buildings have been destroyed by wildfires that remained uncontained Sunday in eastern Washington state.
The leader of Canada's Ontario province on Saturday lashed out at President Donald Trump over his threat to add "the cost of pollution" from that country's wildfires to US tariffs.
Smoke contains fine particles that can travel deep into the lungs.
Heavy smoke from several large wildfires blazing in Canada and Minnesota is expected to engulf large swaths of the Midwest and Northeast U.S. this week, exposing millions of people to dangerous air pollution.
Three firefighters killed over the weekend in a wildfire along the Colorado-Utah border were trying to shield themselves from flames by deploying tent-like shelters when they were overcome, authorities said.