NEW YORK (NewsNation) — Unhealthy air quality alerts continued Thursday as plumes of smoke from over 400 Canadian wildfires blanketed the East Coast, affecting more than 100 million Americans.

New York City officials expected conditions to improve Thursday, but still asked residents to wear N95 masks as a precaution.

However, as those wildfires continue to burn in Canada and with rain not expected in the forecast, the smoke may not begin to fade until sometime next week.

“This is an unpredictable series of events and we cannot provide guidance more than a day in advance at this point,” New York City Mayor Eric Adams said during a press conference on Wednesday.

City health officials warned tiny particles of smoke can cause eye and throat irritation and significant damage to your lungs.

Children and the elderly who have asthma, cardiovascular issues or breathing problems should be especially careful until the smoke dissipates and the air quality improves.

“It feels like someone is sitting on my chest,” Connecticut resident Kassidy Philpott said. “I’ve been super congested. I feel like I can barely breathe.”

Much of the air was in the “unhealthy or worse categories in areas from the mid-Atlantic through the Northeast and parts of the Upper Great Lakes,” according to an advisory issued by the Environmental Protection Agency Wednesday night.

On Wednesday evening, the air quality in New York City hit record levels, reaching 484 on the Air Quality Index, according to Adams. The index tops out at 500 and anything above 301 is considered “hazardous.”

U.S. authorities issued air quality alerts in multiple regions and smoke was expected to persist for days, especially since the weather system is expected to hardly budge. Norwegian officials said the smoke is also expected to pour into Norway on Thursday.

“Conditions are likely to remain unhealthy, at least until the wind direction changes or the fires get put out,” U.S. National Weather Service meteorologist Bryan Ramsey 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.”

Paul Billings from the American Lung Association explained that these really high levels are unsafe for everyone.

“Consider wearing an N95 to protect you from these particles that can penetrate deep into the lungs and cause lung damage, asthma attacks, heart attacks, strokes, very serious health complications — and not just for people with asthma and chronic obstructive pulmonary disease, all are at risk at air pollution levels this high,” Billings said.

He said that symptoms like coughing, wheezing, shortness of breath and burning of the eyes can all be warning signs that people have been exposed to dangerous air pollution.

“Please if you can, we can encourage everyone to stay inside. The best protection is to avoid going outside,” NYC Emergency Management Commissioner Zachary Iscol said.

A time-lapse video showed how quickly smoke took over the city’s iconic skyline. The dramatic color change left people amazed and afraid.

President Joe Biden has deployed more than 600 federal firefighters to Canada to help fight the fires.

“We have already deployed over 600 U.S. firefighters and personnel as well as equipment like water bombers to help Canada battle the fires,” White House press secretary Karine Jeanne-Pierre said.

New York Gov. Kathy Hochul announced that New York has made one million N95 masks available for people who need them.

“Please don’t go out unless you have to. I feel like I say this during a snowstorm as well but this is about your health and your family’s health,” New York Gov. Kathy Hochul said.

The Federal Aviation Association (FAA) announced Thursday that it paused all flights from the Northeast, Ohio and Mid-Atlantic bound for LaGuardia International Airport and Philadelphia International Airport and delayed all flights bound for Newark Liberty International Airport due to the reduced visibility from the wildfire smoke.

Flights were also grounded due to low visibility at Philadelphia International Airport Thursday morning, the FAA tweeted.

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.

The Associated Press and PIX 11 contributed to this report.