New Canadian wildfires have sent a plume of smoke into the United States again

New Canadian wildfires have sent a plume of unhealthy smoke into the United States again.

A recent wildfire in western Canada sent unhealthy smoke into the United States.

Air quality alerts were in effect Saturday in at least eight states across the Northern Plains and upper Midwest as smoke returned from wildfires.

The smoke will be thickest across parts of Montana, the Dakota, Minnesota, and Iowa on Saturday before moving to the southeast later in the weekend. Minneapolis and Des Moines, Iowa, will see the worst smoke on Saturday, while cities like Chicago, St. Louis, Detroit, and Cincinnati will begin to see the effects on Sunday.

The Midwest will continue to see poor air quality and reduced visibility early next week as the smoke persists.

In late June, Chicago experienced some of the worst air quality in the world in thick smog.

This time, the plume of smoke is not coming from the Canadian province of Quebec. Instead, it flows across Canada from far in the west, so it shouldn't reach as far into the northeast as it did in early June when the New York City sky turned an apocalyptic shade of orange.

On Friday, trespassing smoke lowered the air quality in parts of Montana and North Dakota to red, or unhealthy levels in the Air Quality Index, and orange, or suffering for sensitive groups, in Minnesota, according to airnow.gov.

Wildfire smoke contains small pollutants known as particulate matter, or PM 2.5, which can reach the lungs and bloodstream once inhaled. According to the Centers for Disease Control and Prevention, these pollutants often cause difficulty breathing and eye and throat irritation but have also been linked to more serious long-term health problems like lung cancer.

The plume was generated by about 400 fires that have raged in the Canadian province of British Columbia in the past week, about half of which were started by 51,000 lightning strikes from thunderstorms, according to the BC Wildfire Service. Some of those thunderstorms were "dry" or produced irrational amounts of rain to help put out any fires, a serious possibility in a county with some of the worst droughts.

Parts of the United States will be at risk of smoke for the foreseeable future, depending on weather patterns and fire outbreaks, because Canada is experiencing its worst fire season on record. More than 24 million acres have burned so far this year, an area about the size of Indiana.

More than 1,000 fires have broken out in British Columbia since April. The BC Wildfire Service said these fires have burned nearly three times more land than the overall average in British Columbia over the past ten years.

A news release from the firefighters' union said that one firefighter was killed Thursday responding to a blaze near Revelstoke, British Columbia. BC Wildfire confirmed the death to CNN. The firefighter has not been identified.

Prime Minister Justin Trudeau mourned the firefighter on Twitter on Friday.

"The news from British Columbia — that a firefighter bravely fighting a wildfire has lost her life — is heartbreaking," Trudeau said. "At this incredibly difficult time, I send my deepest condolences to her family, friends, and fellow firefighters."