Residents of the northeastern United States were Breathing more easily Friday, as smoke from Canadian fires gradually cleared after blanketing several cities in a noxious haze this week.
The US Environmental Protection Agency classified air quality in New York and Washington as moderate.
In the American capital, the sky was blue again Friday, but as a precautionary measure, children at the city's public schools were still banned from spending recess outdoors.
New York's public schools were closed and operated remotely.
Air quality has improved after winds blowing over the Canadian province of Quebec, where the fires are raging, Ryan Stauffer, a NASA scientist specialising in air pollution, told AFP.
The concentration of fine particles was up to twenty times lower Friday morning in Washington than the same time on Thursday, Stauffer said.
The region was surrounded by thick skies and acrid smell, with air pollution exceeding some of the most contaminated cities in the world in South Asia and China.
Passengers were delayed at many airports due to reduced visibility and masks on the streets.