Smoke from Canadian wildfires is still wafting south. Conditions for some are expected to improve soon

More than 100 million people are under air quality alerts Friday morning from Wisconsin to Vermont and down to North Carolina as smoke from Canadian wildfires continues to waft south, though conditions are expected to improve slowly into the holiday weekend.

Storms Thursday brought some relief from the smoke in parts of the Midwest, and more rain there Friday should provide more. But smoke may dissipate less quickly in the Ohio Valley and the Mid-Atlantic, where Friday’s storms will be more isolated.

“Air quality is expected to improve in the short term as a combination of thunderstorm activity and dispersion of smoke will ultimately result in improving air quality conditions for much of the country heading into the weekend,” the National Weather Service said.

More than 500 active wildfires raging across Canada have tanked the air quality across parts of that country and the United States. As of early Friday, Toronto topped a list of the world’s major cities with the worst air quality, followed by Washington, DC, according to IQAir.

People look out at a hazy Manhattan skyline from the Rockefeller Center viewing deck Friday, June 30, in New York.

Smoke from wildfires in Canada shrouds the view of the Statue of Liberty on Friday in New York.

The setting sun is shrouded by smoke from Canadian wildfires in this photo taken from New York's 42nd Street on Thursday, June 29.

Haze hangs over downtown Pittsburgh and PNC Park as fans take their seats before a Major League Baseball game between the Pittsburgh Pirates and the San Diego Padres on June 29.

Traffic makes its way across the Chesapeake Bay Bridge in Stevensville, Maryland, on June 29.

Smoke and haze is seen from the Lincoln Memorial in Washington, DC, on Tuesday, June 27.

People in Chicago walk along the shoreline of Lake Michigan on June 27.

A Canadian soldier flies over a wildfire near Mistissini, Quebec, on June 12.

Wildfires burn in British Columbia in this aerial photo released by the BC Wildfire Service on June 9.

A jogger wears a face mask in Washington, DC, on June 9.

A man wears a protective face mask while walking through Times Square in New York on June 8.

An airplane takes off June 8 from Ronald Reagan Washington National Airport in Arlington, Virginia.

Traffic heads into Washington, DC, under hazy conditions on June 8.

Smoke from Canadian wildfires obscures the visibility in Pittsburgh on June 8.

Buildings in the Philadelphia skyline are shrouded in smoke on June 8.

A cyclist rides under a blanket of haze that was partially obscuring the US Capitol on June 8.

A woman in New York City wears a mask during the morning rush hour on June 8. The city saw slight air quality improvements, but levels were still considered "very unhealthy" for residents.

The One World Trade Center tower is seen in New York, shortly after sunrise on June 8.

A starting gate is unused at Belmont Park in Elmont, New York, on June 8.

Transit employee Shanita Hancle, left, hands out masks to commuters at a subway station in New York on June 8.

The Philadelphia skyline is shrouded in haze on June 8.

A smoky haze obscures M&T Bank Stadium in Baltimore on June 8.

Firefighters battle a wildfire in Evansburg, Alberta, on June 8.

A person on the New York City subway wears a mask as smoky haze blankets a neighborhood on June 7.

Workers chain up seats at Citizens Bank Park after the Philadelphia Phillies postponed a baseball game because of poor air quality on June 7. The New York Yankees also postponed a game that night.

Two men stand by the waterfront in Brooklyn, New York, on June 7.

Smoky haze affects the visibility of the Empire State Building in New York on June 7.

A man in Piermont, New York, attempts to photograph the sun obscured by smoke on June 7.

Smoke blankets the Lincoln Memorial Reflecting Pool and the National Mall on June 7.

A person in Fort Lee, New Jersey, talks on the phone near the George Washington Bridge on June 7.

Smoke obscures the view from the New York State Thruway, looking north from West Nyack on June 7.

People wear face masks as they walk in New York's Herald Square on June 7.

A woman jogs along the Hudson River as a smoky haze hangs over the New York City skyline shortly after sunrise on June 7.

A couple sits for lunch in Cincinnati on June 6. Smoke from the Canadian wildfires had drifted to the city, causing the air to appear hazy.

People at Toronto's CN Tower take photos of the smoky city on June 6.

The sky is discolored during a New York Yankees baseball game on June 6.

A smoky sky provides a muted backdrop June 6 at Rock Harbor in Massachusetts. Skies over Cape Cod were filled with smoke from the wildfires in Canada.

People in New York wear masks as they ride bikes on June 6. That morning, the city briefly had the world's worst levels of air pollution.

The Statue of Liberty is obscured by the air pollution in New York on June 6.

Wildfire smoke engulfs downtown Ottawa on June 5.

Smoke billows upwards from a planned ignition by firefighters who were tackling the Donnie Creek Complex wildfire south of Fort Nelson, British Columbia, on June 3.

Firefighter Jason Rock sprays hot spots in the Birchtown area while tackling wildfires in Shelburne County, Nova Scotia, on June 3.

An astronaut aboard the International Space Station took this photo of wildfire smoke near Shelburne, Nova Scotia, on May 29. Human-caused climate change has exacerbated the hot and dry conditions that allow wildfires to ignite and grow.

Smoke rises from a wildfire in Fort Nelson on May 27.

Firefighters stand on a truck while battling a blaze near Fort St. John, British Columbia, on May 14.

BJ Fuchs, a farmer who has lost some land and had to move his cattle due to the wildfires, stands in Shining Bank, Alberta, on May 11.

In pictures: Canadian wildfires impact US air quality

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Detroit, which topped the same list on Thursday evening, ranked fourth early Friday, while New York City was sixth, the website showed.

On Friday, the United States’ worst air quality is expected to span from Michigan to Ohio and into the Mid-Atlantic, including Washington, DC.

The air in those areas is expected to be rated a level 3 of 6 “unhealthy for sensitive groups” or a level 4 of 6 “unhealthy” on the US Air Quality Index developed by the US Environmental Protection Agency. Current air quality ratings can be found on AirNow.gov, a partnership of agencies including the EPA.

“Unhealthy for sensitive groups” typically includes the elderly, young children, those with certain chronic illnesses and outdoor workers.

In New York, a statewide air quality health advisory will remain in effect through Friday, urging residents to take necessary preventative measures – like masking – to stay safe outdoors, Gov. Kathy Hochul announced Thursday. “With ground-level smoke more visible and air quality continuing to reach unhealthy levels in many parts of the state, we encourage New Yorkers to take precautions to protect their health,” she said.

The western and central parts of New York along with the eastern Lake Ontario region are forecast Friday to reach the “unhealthy” air quality threshold, the governor’s office said. Other areas in the state could see air rated in the less severe “unhealthy for sensitive groups” category.

Air quality in New York is at unhealthy levels Thursday due to smoke from Canadian wildfires.

An air quality advisory for New York City was extended until 11:59 p.m. on Friday, city officials said, adding that they do not believe the air quality alert will remain in effect through the weekend.

As of Friday afternoon, officials said they don’t anticipate air quality issues hindering Tuesday’s fireworks shows but warn that that assessment could change as air quality can only be forecast a day in advance.

Canada Day fireworks in Montreal canceled

Canada’s Ontario, Quebec and British Columbia provinces had some of that nation’s worst air quality Thursday night, according to IQAir.

The impacts of the fires have prompted Canadian officials to cancel Canada Day fireworks in Montreal scheduled for Saturday, though other festivities are planned.

Rebecca Schmitt told CNN she took this picture at around 1pm in Mattoon, Illinois, and described the clouds as, "awesome looking."

A massive storm is plowing through the Midwest, clearing out smoke with hurricane-force wind gusts

While forecasters weren’t sure about Saturday’s air quality, the cancellation decision was “in solidarity,” said Stéphane Guertin, president of Tandem Communications, the event organizer.

“I am just being compassionate to what is going on right now. So, that is why we are canceling it. It is a question of what is going on in the fires and what is in the air right now,” Guertin told CNN. “There is something bad happening now in the north of Quebec, so we are all together in this. So, it’s been canceled. We are not going to put something more in the air.”

The Toronto skyline is covered by smoke Wednesday at the CN Tower.

Canada is experiencing its worst wildfire season on record, with scientists warning such intense blazes are becoming more common as the planet warms. Smoke from the flames can travel thousands of miles, putting millions more people in harm’s way.

Wildfire smoke is particularly dangerous because it contains particulate matter, or PM2.5, a tiny but dangerous pollutant. When inhaled, it can travel deep into lung tissue and enter the bloodstream, according to the US Centers for Disease Control and Prevention.

It comes from sources including the combustion of fossil fuels, dust storms and wildfires. The particulate matter has been linked to health problems including asthma, heart disease and other respiratory illnesses.

CNN’s Michelle Watson and Raja Razek contributed to this report.