Smoke from Canadian wildfires has been drifting south into the United States, affecting air quality for millions of people from the Midwest to the East Coast.

Canada is seeing its worst fire season on record. At least 19 million acres have been charred across the country.

"Year after year, with climate change, we're seeing more and more intense wildfires and in places where they don't normally happen," Canadian Prime Minister Justin Trudeau said in a news conference in early June.

Smoke from wildfires in Canada shrouds the view of the Statue of Liberty on Friday in New York.
Smoke from wildfires in Canada shrouds the view of the Statue of Liberty on Friday in New York.
David Dee Delgado/Getty Images North America/Getty Images
The setting sun is shrouded by smoke from Canadian wildfires in this photo taken from New York's 42nd Street on Thursday, June 29.
The setting sun is shrouded by smoke from Canadian wildfires in this photo taken from New York's 42nd Street on Thursday, June 29.
Gary Hershorn/Corbis News/Getty Images
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.
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.
Gene J. Puskar/AP
Traffic makes its way across the Chesapeake Bay Bridge in Stevensville, Maryland, on June 29.
Traffic makes its way across the Chesapeake Bay Bridge in Stevensville, Maryland, on June 29.
Jim Watson/AFP/Getty Images
Smoke and haze is seen from the Lincoln Memorial in Washington, DC, on Tuesday, June 27.
Smoke and haze is seen from the Lincoln Memorial in Washington, DC, on Tuesday, June 27.
Megan Smith/USA Today Network
People in Chicago walk along the shoreline of Lake Michigan on June 27.
People in Chicago walk along the shoreline of Lake Michigan on June 27.
Kamil Krzaczynski/AFP/Getty Images
A Canadian soldier flies over a wildfire near Mistissini, Quebec, on June 12.
A Canadian soldier flies over a wildfire near Mistissini, Quebec, on June 12.
Cpl Marc-Andre Leclerc/Canadian Forces/Reuters
Wildfires burn in British Columbia in this aerial photo released by the BC Wildfire Service on June 9.
Wildfires burn in British Columbia in this aerial photo released by the BC Wildfire Service on June 9.
Xinhua/Shutterstock
A jogger wears a face mask in Washington, DC, on June 9.
A jogger wears a face mask in Washington, DC, on June 9.
Drew Angerer/Getty Images
A man wears a protective face mask while walking through Times Square in New York on June 8.
A man wears a protective face mask while walking through Times Square in New York on June 8.
Shannon Stapleton/Reuters
An airplane takes off June 8 from Ronald Reagan Washington National Airport in Arlington, Virginia.
An airplane takes off June 8 from Ronald Reagan Washington National Airport in Arlington, Virginia.
Saul Loeb/AFP/Getty Images
Traffic heads into Washington, DC, under hazy conditions on June 8.
Traffic heads into Washington, DC, under hazy conditions on June 8.
Matt McClain/The Washington Post/Getty Images
Smoke from Canadian wildfires obscures the visibility in Pittsburgh on June 8.
Smoke from Canadian wildfires obscures the visibility in Pittsburgh on June 8.
Emmalee Reed/CNN
Buildings in the Philadelphia skyline are shrouded in smoke on June 8.
Buildings in the Philadelphia skyline are shrouded in smoke on June 8.
Hannah Beier/Bloomberg/Getty Images
A cyclist rides under a blanket of haze that was partially obscuring the US Capitol on June 8.
A cyclist rides under a blanket of haze that was partially obscuring the US Capitol on June 8.
Mandel Ngan/AFP via Getty Images
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.
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.
Timothy A. Clary/AFP via Getty Images
The One World Trade Center tower is seen in New York, shortly after sunrise on June 8.
The One World Trade Center tower is seen in New York, shortly after sunrise on June 8.
Mike Segar/Reuters
A starting gate is unused at Belmont Park in Elmont, New York, on June 8.
A starting gate is unused at Belmont Park in Elmont, New York, on June 8.
John Minchillo/AP
Transit employee Shanita Hancle, left, hands out masks to commuters at a subway station in 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.
Seth Wenig/AP
The Philadelphia skyline is shrouded in haze on June 8.
The Philadelphia skyline is shrouded in haze on June 8.
Matt Rourke/AP
A smoky haze obscures M&T Bank Stadium in Baltimore on June 8.
A smoky haze obscures M&T Bank Stadium in Baltimore on June 8.
Ting Shen/Bloomberg via Getty Images
Firefighters battle a wildfire in Evansburg, Alberta, on June 8.
Firefighters battle a wildfire in Evansburg, Alberta, on June 8.
Alberta Wildfire/EPA-EFE/Shutterstock
A person on the New York City subway wears a mask as smoky haze blankets a neighborhood on June 7.
A person on the New York City subway wears a mask as smoky haze blankets a neighborhood on June 7.
David Dee Delgado/Getty Images
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.
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.
Matt Slocum/AP
Two men stand by the waterfront in Brooklyn, New York, on June 7.
Two men stand by the waterfront in Brooklyn, New York, on June 7.
Amr Alfiky/Reuters
Smoky haze affects the visibility of the Empire State Building in New York on June 7.
Smoky haze affects the visibility of the Empire State Building in New York on June 7.
David Dee Delgado/Getty Images
A man in Piermont, New York, attempts to photograph the sun obscured by smoke on June 7.
A man in Piermont, New York, attempts to photograph the sun obscured by smoke on June 7.
John Meore/The Journal News/USA Today Network
Smoke blankets the Lincoln Memorial Reflecting Pool and the National Mall on June 7.
Smoke blankets the Lincoln Memorial Reflecting Pool and the National Mall on June 7.
Leah Millis/Reuters
A person in Fort Lee, New Jersey, talks on the phone near the George Washington Bridge on June 7.
A person in Fort Lee, New Jersey, talks on the phone near the George Washington Bridge on June 7.
Seth Wenig/AP
Smoke obscures the view from the New York State Thruway, looking north from West Nyack on June 7.
Smoke obscures the view from the New York State Thruway, looking north from West Nyack on June 7.
Peter Carr/The Journal News/USA Today Network
People wear face masks as they walk in New York's Herald Square on June 7.
People wear face masks as they walk in New York's Herald Square on June 7.
Yuki Iwamura/AP
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 woman jogs along the Hudson River as a smoky haze hangs over the New York City skyline shortly after sunrise on June 7.
Mike Segar/Reuters
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.
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.
Kareem Elgazzar/The Cincinnati Enquirer/USA Today Network
People at Toronto's CN Tower take photos of the smoky city on June 6.
People at Toronto's CN Tower take photos of the smoky city on June 6.
Carlos Osorio/Reuters
The sky is discolored during a New York Yankees baseball game on June 6.
The sky is discolored during a New York Yankees baseball game on June 6.
Frank Franklin II/AP
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.
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.
Merrily Cassidy/Cape Cod Times/USA Today Network
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.
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.
Selcuk Acar/Anadolu Agency via Getty Images
The Statue of Liberty is obscured by the air pollution in New York on June 6.
The Statue of Liberty is obscured by the air pollution in New York on June 6.
Amr Alfiky/Reuters
Wildfire smoke engulfs downtown Ottawa on June 5.
Wildfire smoke engulfs downtown Ottawa on June 5.
Spencer Colby/The Canadian Press via AP
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.
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.
B.C. Wildfire Service via Reuters
Firefighter Jason Rock sprays hot spots in the Birchtown area while tackling wildfires in Shelburne County, Nova Scotia, on June 3.
Firefighter Jason Rock sprays hot spots in the Birchtown area while tackling wildfires in Shelburne County, Nova Scotia, on June 3.
Communications Nova Scotia via Reuters
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.
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.
NASA
Smoke rises from a wildfire in Fort Nelson on May 27.
Smoke rises from a wildfire in Fort Nelson on May 27.
B.C. Wildfire Service via Reuters
Firefighters stand on a truck while battling a blaze near Fort St. John, British Columbia, on May 14.
Firefighters stand on a truck while battling a blaze near Fort St. John, British Columbia, on May 14.
Kamloops Fire Rescue via Reuters
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.
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.
Anne-Sophie Thill/AFP via Getty Images