President Donald Trump on Friday threatened to impose new tariffs on Canada, saying the costs of wildfire smoke polluting American cities would be added to existing trade duties, as hundreds of fires burned across the country and smoke drifted across the northern United States.
Trump, writing on Truth Social, accused Canada of “willful negligence” and failing to properly maintain its forests and brush. “The United States is being unnecessarily invaded by filthy, polluted, and unhealthy air,” he wrote. He said he planned to call Canadian Prime Minister Mark Carney later Friday to demand an explanation. The billions of dollars in costs inflicted on the U.S. by the air pollution “must of necessity be added to the TARIFFS Canada is currently paying,” Trump wrote.
The threat escalates an already tense relationship. Trade between the two countries has been strained for over a year. Both nations have yet to reach a trade deal after Trump imposed tariffs on Canada last year, ending decades of free trade. As of Friday, about 888 fires were actively burning in Canada, according to the Canadian Wildland Fire Information System, with the majority burning out of control. Nearly 3 million hectares of land have been destroyed. More than 190 of those blazes are in Ontario, some out of control.
Smoke has spread across U.S. states from Minnesota and Michigan to Pennsylvania, Ohio, and New York, triggering “hazardous” air quality alerts and forcing the cancellation of outdoor events. Detroit had the worst air quality in the world on Friday, according to the Swiss air quality tracker IQAir. Chicago ranked second. Washington, D.C., and New York placed seventh.
A blame game across the border
Republican lawmakers from Michigan sent an open letter to Canadian officials declaring their “patience has run out.” John James, John Moolenaar, Jack Bergman, and Lisa McClain wrote that they were “done accepting apologies in place of action,” warning the U.S. could explore direct involvement in cross-border wildfire protection if Canada failed to act. They cited “chronic under-investment in forest thinning, fuel reduction, and prescribed burns, along with inadequate enforcement against arson” as unaddressed problems.
Some Republicans used the issue to renew Trump’s call to make Canada the 51st U.S. state, a proposal that has offended Canadians and prompted many to stop traveling to their southern neighbor in protest. Others online suggested delaying the opening of the Gordie Howe International Bridge, a Canada-funded project connecting Ontario to Michigan.
Ontario Premier Doug Ford fired back. “Maybe what you should do rather than complain is send support, send help, because we have done the exact same thing for our American friends,” Ford said Friday, noting that Canada has helped the U.S. battle wildfires in California and respond to hurricanes in North Carolina. He said the U.S. states of Michigan and Massachusetts, both led by Democrats, have offered assistance with water bombers, firefighters, and rescue operations. “We are throwing every single resource we can,” Ford said.
Carney said climate change is everyone’s responsibility, including the United States. His emergency management cabinet minister said the two countries remain in constant contact, citing a reciprocal firefighting agreement from 1982 and another assistance agreement that emerged from the 2025 G7 summit. MP Eleanor Olszewski said Canada has invested about C$12 billion ($8.5 billion; £6.4 billion) in forest sustainability and fire prevention. “This is a challenge that knows no borders, and Canada is working with speed, collaboration and coordination to keep people safe,” she said.
Scientists say the picture is more complicated
Scientists caution that the situation is not as simple as the political rhetoric suggests. “Weather doesn’t care about international borders,” said Dr. Patrick James of the University of Toronto. Once smoke reaches the atmosphere, it travels wherever winds take it, and smoke from major U.S. wildfires has also affected Canada in recent years. Experts note that many of the current fires are burning in Canada’s vast, remote forests, where fires can be difficult to detect or contain before they grow too large. Better forest management can reduce wildfire risk near communities, but it cannot prevent fires across a landscape of this scale.
Wildfires are common in Canada. But the number of outbreaks has rapidly increased in recent weeks. Scientists in both countries agree that increasingly severe wildfire seasons are being driven in part by climate change, which creates hotter, drier conditions that allow fires to spread more easily. Carney, in an X post Wednesday, said the wildfires have “escalated significantly” in recent weeks, particularly in Northwestern Ontario, where thousands of people have been forced to evacuate.
The poor air quality has raised questions about potential impacts on the FIFA World Cup final, set for Sunday in northeastern New Jersey between Spain and Argentina. Trump, who is scheduled to attend the match, traveled to New York City on Friday for a FIFA reception at Trump Tower. EPA Administrator Lee Zeldin said Friday that the “impacts of the Canadian wildfires are causing great concern and harm across the United States.” The EPA is in communication with Canada’s leadership and will “strongly encourage them to do everything in their power to extinguish these fires as fast as possible,” Zeldin wrote on X.
Shortly after Trump’s post, The New York Times reported that the Trump administration has moved in recent months to dismantle government labs researching wildfire smoke and its effects. Scientists have warned that human-influenced climate change is leading to more wildfires and other extreme weather events.