A dense cloud of smoke from the hundreds of wildfires burning in Canada covered much of the US northeast and southern Canada on Thursday, sharply worsening air quality in cities such as New York, Chicago, Detroit, and Toronto. Health authorities advised residents to stay indoors, three days before New Jersey's MetLife Stadium hosts the World Cup final between Spain and Argentina.

New York City has been dealing with a "Code Red" due to the heat and air quality advisories from Canadian wildfire smoke days before the Spain-Argentina World Cup final.

As thick smoke settles in over major cities, Canada recorded the worst air quality in the world.

Authorities issue health warnings after smoke from wildfires in Canada envelops north-eastern US