More than 900 wildfires are burning across Canada, including in the provinces of Manitoba and Ontario, and the smoke has pushed air quality into unhealthy ranges across a broad stretch of the United States for much of the past week. President Donald Trump responded on Friday by threatening to add the cost of the pollution to the tariffs Canada already pays.
Writing on Truth Social, Trump accused Canada of failing to maintain its forests and said the United States was being "invaded by filthy, polluted, and unhealthy air." He called it "Willful Negligence, and becoming a yearly occurrence, costing the United States Billions of Dollars, which cost of this pollution must of necessity be added to the TARIFFS Canada is currently paying."
The air quality effects have been widespread. Index readings climbed into unhealthy territory in Detroit and Chicago as smoke spread south, and Minnesota recorded the most intense smoke pollution in its history, with fires burning in and near the Boundary Waters adding to the Canadian plumes. Poor air persisted across the Northeast, Mid-Atlantic and Midwest into Saturday.
The National Weather Service said heavy rain and storms would help clear the air across the Northeast and Mid-Atlantic over the weekend, while dangerous pollution levels would linger over the Midwest. Conditions in the Northeast were improving by Saturday.
The threat has no obvious instrument behind it. Tariffs apply to goods entering a customs territory; smoke crosses the border without a shipper, a value or a tariff line, and no existing US trade authority prices an airborne pollutant into a duty rate. Any attempt to do so would sit awkwardly alongside the tariffs already in force between the two countries, which are the subject of a continuing dispute.
The grievance itself is not new. This is the second consecutive summer in which smoke from Canadian fires has driven American air quality to record-poor readings, and the boreal forest where most of the fires burn is warming faster than the global average, lengthening the season in which it can burn. Canada's fire agencies have consistently attributed the scale of recent seasons to hotter, drier conditions rather than to a change in forest management.
For the northeastern United States the timing carried an added consequence: the World Cup final is scheduled for Sunday afternoon at MetLife Stadium in New Jersey, and air quality and storm forecasts have been part of the build-up all week.