NYC engulfed in wildfire smoke in stunning time-lapse footage.

Smoke from hundreds of active wildfires in Canada caused the worst air quality in New York City since the 1960s, with visibility deteriorating rapidly throughout Wednesday afternoon. The National Weather Service posted a time-lapse video on Twitter showing the city skyline fading into an orange haze. The air quality index was even worse than after the 9/11 attacks, but the air from the Canadian wildfires is not as toxic as the debris cloud that shrouded the city after the World Trade Center towers collapsed. Officials warned those vulnerable to poor air quality to limit time outdoors, and the city is distributing masks. Schools may be closed on Friday depending on air quality.