More than 850 active fires in Canada, smoke spreading to the United States

Some 857 wildfires are burning simultaneously in Canada, including 23 declared on Thursday. Toxic smoke is now spreading to the northern United States, prompting air quality alerts from Michigan to New York.

Canada is facing a relentless fire crisis: according to the Canadian Interagency Forest Fire Centre, 857 fires were active on Thursday, the vast majority out of control according to the Canadian Forest Fire Information System. Twenty-three new fires broke out on Thursday alone.

The concentration of fires in northwestern Ontario is generating thick plumes of smoke that are blanketing Thunder Bay and Toronto before crossing the Great Lakes into the United States. The U.S. National Weather Service (NOAA) has issued alerts covering the upper Midwest, the Great Lakes region, and the northeastern United States.

In Michigan and Minnesota, air quality is classified as "hazardous" by the US AQI index, the highest level, with a recommendation to stay indoors. In Detroit, air quality was the worst in the world on Thursday according to the Swiss air quality monitoring network IQAir, ahead of Minneapolis and Toronto. In western New York State, the air is considered "very unhealthy," while the New York metropolitan area is classified as "unhealthy."

New York City activated its emergency air quality protocols on Wednesday and expanded its heat wave plans, opening hundreds of cooling centers and distributing KN95 masks across the city.

Northwest winds are expected to continue pushing smoke toward the northern U.S. states for the rest of the week and through the weekend. There is particular concern for New Jersey, where the World Cup final is scheduled for Sunday. A change in wind direction expected on Monday should direct the smoke toward Quebec, bringing gradual improvement to the south.

In Ontario, thunderstorms are forecast for the coming days, but the rainfall may prove insufficient to significantly change the situation.

On a human level, the fires in northern Ontario have forced hundreds of First Nations community members to flee, some by boat from remote areas. Grand Chief Linda Debassige of the Anishinabek Nation Council indicated in a statement that homes and buildings had sustained significant damage. A video released Wednesday showed a Canadian National freight train surrounded by flames near Armstrong; the trapped railway workers were eventually rescued, and the company has temporarily suspended its operations in the region.

On the diplomatic front, Republican lawmakers from Michigan sent an open letter to Canadian Prime Minister Mark Carney calling for improved management of wildfires. "A year has passed, the season has returned, and nothing has changed except that our patience has run out," wrote the four signatories. The U.S. ambassador to Canada, Pete Hoekstra, adopted a more measured tone on Wednesday, praising the joint efforts of the two countries: "This challenge knows no borders. The United States will continue to coordinate closely with Canada, as we have for more than 40 years in the face of wildfire emergencies."