Wildfire smoke from Ontario has severely degraded air quality across the northeastern United States. Chicago recorded "Very Unhealthy" levels of fine particulate pollution on Wednesday. Toronto briefly ranked as the world's most polluted major city while New York issued alerts. Health advisories urge residents to reduce strenuous outdoor activities as smoke spreads. Authorities continue monitoring air quality as wildfire smoke shifts with weather patterns.

Wildfires in Canada are pouring thick clouds of smoke into the US and will usher in unhealthy air quality for millions of people in Northeast and Midwest.

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.

A massive plume of smoke from wildfires burning across Canada has swept into the United States, degrading air quality across the Midwest, Northeast and Mid-Atlantic.