Canadian wildfires drive smoke into U.S., with no letup expected soon

New York's La Guardia Airport issued a ground stop early Thursday as the weather system that's driving the ongoing Canadian-American smoke out — a low-pressure system over Maine and Nova Scotia — "will probably be hanging around at least for the next few days," according to a U.S. National Weather Service meteorologist.

"Conditions are likely to remain unhealthy, at least until the wind direction changes or the fires get put out," Brian Ramsey of the NWS said. "Since the fires are raging — they're really large — they're probably going to continue for weeks. But it's really just going be all about the wind shift."

That means at least another day, or more, of a dystopian-style detour that's chased players from ball fields, actors from Broadway stages, delayed thousands of flights and sparked a resurgence in mask wearing and remote work — all while raising concerns about the health effects of prolonged exposure to such bad air.

Across the eastern U.S., officials warned residents to stay inside and limit or avoid outdoor activities again Thursday, extending "Code Red" air quality alerts in some places for a third straight day as forecasts showed winds continuing to push smoke-filled air south.

La Guardia Airport advised of a ground stop early Thursday of flights bound for San Francisco and Newark, N.J., due to low visibility. The Federal Aviation Administration in D.C. said flights from the Northeast, Ohio and Mid-Atlantic sections of the U.S. bound for La Guardia had been paused.

"Reduced visibility from wildfire smoke will continue to impact air travel today. We will likely need to take steps to manage the flow of traffic safely into New York City, D.C., Philadelphia and Charlotte," the FAA said, advising travellers who might be affected to check their website for updates.

Plumes of fine particulate matter were experienced as far south as North Carolina. Health officials from Vermont to South Carolina and as far west as Ohio and Kansas warned residents that spending time outdoors could cause respiratory problems due to high levels of fine particulates in the atmosphere.

In Washington, D.C., Mayor Muriel Bowser ordered schools to cancel outdoor recess, sports and field trips Thursday. In suburban Philadelphia, officials set up an emergency shelter so people living outside can take refuge from the haze.

New York Gov. Kathy Hochul said the state was making a million N95 masks — the kind prevalent at the height of the COVID-19 pandemic — available at state facilities, including 400,000 in New York City. She also urged residents to stay put.

"You don't need to go out and take a walk. You don't need to push the baby in the stroller," Hochul said Wednesday night. "This is not a safe time to do that."

The message may be getting through. So far, officials said Wednesday, New York City has yet to see an uptick in 911 calls related to respiratory issues and cardiac arrests.

More than 400 blazes burning across Canada have left 20,000 people displaced. The U.S. has sent more than 600 firefighters and equipment to Canada, among the countries that are helping in the effort to tamp the fires.

Prime Minister Justin Trudeau spoke to U.S. President Joe Biden by phone on Wednesday. Trudeau's office said he thanked Biden for his support and that both leaders "acknowledged the need to work together to address the devastating impacts of climate change."

Biden also urged affected residents to follow guidelines set by local officials to stay safe.