Pictures: Canadian wildfires affect US air quality.

On Wednesday, June 7, a smoky haze covered a New York City neighborhood, prompting one subway rider to don a mask.

Millions of people in the Northeast, Midwest, 

and Mid-Atlantic have had their air quality negatively impacted by smoke from wildfires in Canada that has been drifting south into the United States.

On June 6th, the air quality index in New York City reached over 200,

which is considered "very unhealthy" for human health.

This year's wildfires in Canada have scorched over 9 million acres,

roughly 15 times the average burned area for this time of year.

Canadian Prime Minister Justin Trudeau recently stated that extreme wildfires are becoming more frequent and widespread across the country as a direct result of climate change.