More than a dozen U.S. states were under air-quality alerts on Wednesday as smoke from hundreds of Canadian wildfires wafted south, casting a dull gray pallor over city skylines and prompting officials to urge residents to remain indoors.
Health officials from Vermont to South Carolina along the East Coast, as well as in Ohio and Kansas in the Midwest, urged millions of residents to limit their time outdoors, warning that fine particulates in the atmosphere could make breathing difficult and pose health risks.
The U.S. National Weather Service issued quality air alerts from New England to South Carolina.
"Wearing a mask may help limit irritation for those suffering from respiratory illnesses," the agency's Washington, D.C.-area office wrote on Twitter. "More smoke expected Thursday & Friday."
Schools up and down the East Coast canceled outdoor activities, including sports practices, field trips and recesses, to protect students from the haze.
In Bethesda, Maryland, a high school moved its graduation ceremony indoors, while a Brooklyn, New York, elementary school postponed its "Spring Fling" dance party. A school in Montclair, New Jersey, called off a fifth-grade trip to a Six Flags amusement park.
New York City's public schools were open for class, although outdoor events and activities, including a middle school graduation, were canceled, postponed or moved indoors.
The smoke is crossing the U.S. northern border from Canada, where wildfire season got off to an unusually early and intense start due to persistent warm and dry conditions. Canada is on track for its worst-ever wildfire season.
The skies above New York and many other North American cities were a uniform gray, and the air smelled like burning wood. In many places, the early morning sun appeared as a small glowing orange disc. New York City's skyscrapers, which can be seen for miles away on a clear day, were rendered nearly invisible.
As of Wednesday morning, New York had the second-worst air quality in world, according to a ranking of major cities by Swiss air quality technology company IQAir, with Delhi, India's smog-plagued capital city, topping the list.
Rochester, New York, near the Canadian border, had the worst air quality in the country, according to IQAir, while six towns along Maryland's Eastern Shore and Delaware were ranked in the bottom 10 for air quality.
Wildfire smoke has been linked with higher rates of heart attacks and strokes, increases in emergency room visits for asthma and other respiratory conditions, and eye irritation, itchy skin and rashes, among other problems.
A Home Depot in Manhattan sold out of air purifiers and masks as residents scrambled to protect themselves from the hazy conditions.
"This is an unprecedented event in our city and New Yorkers must take precaution," New York City Mayor Eric Adams said.
Canadian authorities on Wednesday issued a starker air-quality warning for the residents of the country's financial capital Toronto due to several raging wildfires that have burned through a record area this year.
While wildfires are common in Canada's West, there are blazes in nearly all of the country's 10 provinces and territories, with Quebec the worst affected at present.
About 3.3 million hectares have already burned - some 13 times the 10-year average - and more than 120,000 people have been at least temporarily forced out of their homes.
