The US Air Quality Index for New York hit 222 on its 0-500 scale at 01:05 a.m.
New York was the most polluted major city in the world on Tuesday night, as smoke from Canadian wildfires blanketed the city in haze, according to the IQAir website.
Pollution levels in the city were deemed to be in the "unhealthy" range, and were higher than those in the Indian capital Delhi and Iraq's Baghdad at 1:25 a.m. New York time, according to the Swiss air quality company.
Other North American cities were also being afflicted by smoke from the unprecedented wildfires, with Detroit affected particularly badly.
New York City Mayor Eric Adams said in a statement Tuesday night that an Air Quality Health Advisory had been issued for all five boroughs, and while conditions were expected to improve through Wednesday morning, they were predicted to worsen again later in the day.
Buildings shrouded in smoke from Canada wildfires beyond the Manhattan Bridge in New York
"We are taking precautions out of an abundance of caution to protect New Yorkers' health until we are able to get a better sense of future air quality reports," said Adams. "We recommend all New Yorkers limit outdoor activity to the greatest extent possible."
The US Air Quality Index for New York hit 222 on its 0-500 scale at 01:05 a.m., putting the air in the "very unhealthy" category.
Canada is on track for its worst ever wildfire season if the rate of burning continues at the same pace. Government officials say approximately 3.3 million hectares (8.2 million acres) have so far been scorched. Some 413 fires are currently burning and 26,000 Canadians have been forced to evacuate their homes.