The hazardous and unhealthy air quality levels that have engulfed Northeast states are becoming more concentrated in the mid-Atlantic region, as the smoke from Canada's wildfires continues to disrupt daily life for tens of millions of people.
The smoky conditions, which turned the skies orange in New York and surrounding areas this week, were worse Thursday morning in places such as Philadelphia, Baltimore and Washington, D.C., according to AirNow, a government tracking site. The Philadelphia area and parts of eastern Pennsylvania appeared the most heavily affected.
Air quality is still expected to be unhealthy in the Northeast for a third straight day as the smoke is lingering above, said Cody Ledbetter, a meteorologist at the National Weather Service in Baltimore and Washington, D.C.
The conditions have halted operations across the Northeast, with some flights being delayed because of the low visibility and with school officials altering schedules to keep children inside in places such as Baltimore and Philadelphia.
Western winds this weekend are expected to move some smoke out of the big metropolitan areas in the Northeast, he said. Conditions in the East should improve early next week as winds from the West push the smoke off the East Coast, Ledbetter said.
"I'm not saying this is completely it," he said, "but we could get some relief next week because of a wind shift."
Still, as long as there are fires burning in Canada, the U.S. will be vulnerable to the smoke when winds carry it south, Ledbetter said.
Officials from multiple states extended health advisories until at least midnight Thursday, encouraging residents from Massachusetts to North Carolina were advised to limit outdoor activities and mask up.
The smoke was forecast to move toward the southern half of the U.S. Friday, according to AirNow. The air quality was expected to be unhealthy for sensitive populations in the Carolinas and in parts of Georgia, Texas and Oklahoma. Most of the Northeast was forecast to have moderate air-quality levels.
More than 40 million people live in areas that had air quality rated unhealthy or worse Wednesday, according to AirNow. The air-quality reading for the New York City area at one point Wednesday surpassed 400-well into the "hazardous" range that calls for all people to stay inside and reduce physical activity, AirNow said. An air-quality level above 300 is considered hazardous.
On Thursday morning, New York City's air-quality reading was 188, which is considered unhealthy but not hazardous, according to AirNow.
New York City Mayor Eric Adams said weather models called for improvement, but there was a possibility that a wind coming from the ocean would push in another harmful plume by Thursday afternoon. Conditions will be worse near the ocean and in southern parts of the city, he said.
"It would be great to see the sun again, but the wind is going to determine that," he said.
At the corner of 48th and Broadway in Midtown, Amir Alhag manned a pushcart selling hot dogs, corn dogs and skewers. He said business took a hit Wednesday because of the smoke clogging the air, which exacerbated his asthma and forced him to take breaks to sit down more than he normally would.
Thursday morning's clearer skies had him going maskless. "Today I'm not scared; today is good," he said.
Higher up on Manhattan, at the corner of 108th Street and Broadway, the line was out-the-door, as it often is, at Absolute Bagels, where locals and visitors alike queued up. Some wore masks but many didn't.
Molly Whelan, who is from Dublin, said she arrived in the city Wednesday during the height of the day's smokiness. The 24-year-old said "it's a bit like being in a 'Blade Runner' film, or 'Dune.'"
Customers in line traded descriptions of Wednesday's orange skies.
"I thought revelation was about to go down," said Michael Adelson, 31, of Queens.
Abdullah Aciker, who runs a produce stand on the corner of 181st Street and Broadway, said the pandemic didn't keep him home and neither will the lingering smoke. Its smell hung heavy in the air Thursday morning as Aciker calculated what customers-many of them masked-owed for the cherries, mangoes, garlic and mushrooms they wanted to buy.
"The community needs its fruits," said Aciker, a 50-year-old father of three.
Many Americans didn't realize fires have been burning in Canada for weeks until their own skies turned orange this week. The smoky skies and thick air rattled parts of the country unaccustomed to dealing with the lingering effects of widespread wildfires.
The Federal Aviation Administration on Thursday paused flights from the Northeast, Ohio and mid-Atlantic bound for New York's LaGuardia Airport, and later said it would continue to slow flights to the airport.
The FAA also briefly halted flights from the Northeast, mid-Atlantic and Ohio bound for Philadelphia, and slowed all departures to Newark Liberty International Airport. The agency said conditions were evolving rapidly, and it would likely need to take steps to manage the flow of traffic into New York, Philadelphia, Washington, D.C., and Charlotte, N.C.
United Airlines said it would waive change fees and fare differences for travelers with flights scheduled Thursday or Friday to a dozen airports in the region who want to change their plans. A Delta Air Lines spokesman said the carrier may proactively cancel some flights to prevent congestion at airports.
Broadway shows including "Hamilton" and "Camelot" canceled performances in New York City on Wednesday, citing the poor air quality for the actors. Home games for the New York Yankees and Philadelphia Phillies Major League Baseball teams were postponed. A WNBA basketball game in Brooklyn was also postponed.
New York Gov. Kathy Hochul said that one million N95-style face masks would be made available to the public. Some will be distributed by local governments, and others will be made available at state facilities, including parks and subway stations.
The Belmont Stakes thoroughbred horse race will take place Saturday on Long Island if the air-quality index is below 200, Hochul said.
"It's going to be a last-minute decision, I'm sure," she said, adding that horse training and exercising were halted Wednesday and Thursday.
Adams said he looked forward to marching in the National Puerto Rican Day Parade on Sunday in Manhattan, if conditions allow.
Canada's wildfire season is off to a blistering start this year, with more than 400 active fires burning in the country, according to the country's natural-resources department. The country could be on track for its most destructive wildfire season ever, officials warned. Wildfires like the ones in Canada are becoming bigger and more frequent as the warming climate dries forests around the world.
Air pollution can be particularly dangerous to children and those with underlying health conditions such as asthma and heart disease.
"We're experiencing a pretty serious health threat from air pollution across really a wide swath of the U.S.," said Paul Billings, national senior vice president of public policy at the American Lung Association. "I think the important thing for people to do during this crisis is to take extra care to protect themselves."
Short-term exposure-a timeline of days to weeks-is associated with increased risk of exacerbating pre-existing respiratory conditions such as asthma, according to the Environmental Protection Agency.
Such exposure can also lead to coughing and difficulty breathing, as well as reduced lung function, heart attack, stroke and increased risk of emergency-room visits and hospital admissions, the EPA said.
Dr. Lauren Zajac, a pediatrician and associate professor of environmental medicine and public health at the Icahn School of Medicine at Mount Sinai, advised people to close windows and doors.
Children should stay inside if possible, she said.
"If you're outside and the mask isn't completely sealed, you'll just breathe in more of the smoke," she said.
Write to Gareth Vipers at gareth.vipers@wsj.com and Alyssa Lukpat at alyssa.lukpat@wsj.com