Updated Jun 30, 2023 - Science

In photos: Canadian wildfire smoke stretches across U.S. and into Europe

Marine One, with President Biden on board, flies past the Jefferson Memorial amid hazy wildfire smoke on June 29 in Washington, D.C., as the city is under a "Code Red" air quality alert. Photo: Chip Somodevilla/Getty Images

Air quality alerts were issued in cities across some 23 U.S. states Thursday as lingering smoke from Canada's worst-ever wildfire season continued to pose a health threat to millions of Americans.

The big picture: Detroit, D.C., New York City and Toronto endured some of the world's worst air quality Thursday, per Swiss air technology company IQAir. Alerts stretched from Colorado to Vermont and down to Georgia. Canadian officials warn this extreme weather event will likely last all summer as climate change leads to more instances of critical fire weather.

A screenshot of an NWS tweet, saying: "Wildfire smoke leads to hazy skies across much of the region today.  An Air Quality Alert is in effect for all of NY and NJ. Individuals sensitive to air quality, including the elderly and the young, should limit strenuous activities and their time outdoors."
Photo: National Weather Service New York/Twitter
Due to the continued affects of the Canadian wildfires, it was another hazy morning in the Twin Cities on Thursday, June 29, 2023. This is looking down the Mississippi River, from Minneapolis towards St. Paul. Canada wildfire smoke affecting Minnesota air quality.
Looking down the Mississippi River, from Minneapolis towards St. Paul, it's another hazy day in the Twin Cities on June 29 due to the continued affects of the Canadian wildfires. Photo: Deb Pastner/Star Tribune via Getty Images
Wildfire smoke obscures the view of the skyline on June 29, 2023 in Chicago, Illinois. The Chicago area is under an air quality alert as smoke from Canadian wildfires has covered the city for a third day in a row.
Wildfire smoke obscures the view of the skyline in Chicago, Illinois, amid an air quality alert as smoke from the hundreds of wildfires in Canada covers the city for a third day in a row on June 29. Photo: Scott Olson/Getty Images
View of the city from the Giralda where you can see the consequences of smoke from the fires in Canada, June 29, 2023 in Seville, (Andalusia, Spain).
A view from Seville, Spain, of smoke from Canada's fires on June 29. Photo : Francisco J. Olmo/Europa Press via Getty Images
The sun setting over the sea is seen through a yellowish cloud of smoke provoked by huge forest fires affecting Canada, across the Atlantic Ocean on June 29, 2023 in Cascais, Portugal.
The sun setting in Cascais, Portugal, on June 29 amid a cloud of smoke that's traveled across the Atlantic Ocean from Canada's fires. Photo: Horacio Villalobos#Corbis/Corbis via Getty Images
 ferry passes as the air quality is at unhealthy levels due to smoke from Canadian wildfires in New York, United States on June 29, 2023. Officials stated that the air quality may worsen in the upcoming days.
A ferry passes as the air quality reaches unhealthy levels due to smoke from Canadian wildfires in New York City on June 29. Photo: Selcuk Acar/Anadolu Agency via Getty Images
A group of people wear face masks to protect against air pollution as they walk past the U.S. Supreme Court Building on June 29, 2023 in Washington, DC. The Washington DC region is under a "Code Red" air quality alert today due to smoke from Canadian wildfires.
A group of people wear face masks to protect against air pollution as they walk past the U.S. Supreme Court in Washington, D.C., on June 29. Photo: Anna Moneymaker/Getty Images
People carry on with their daily lives as the air quality is at unhealthy levels due to smoke from Canadian wildfires in New York, United States on June 29, 2023. Officials stated that the air quality may worsen in the upcoming days.
People carry on with their daily lives as the air quality reaches unhealthy levels due to smoke from the Canadian wildfires in New York City on June 29. Photo: Fatih Aktas/Anadolu Agency via Getty Images
A screenshot of a tweet by NWS Baltimore-Washington saying: "Dry and hazy conditions will continue into tonight. Low temperatures will fall into the 60s for most locations."
Photo: NWS Baltimore-Washington/Twitter
A blanket of smoke from wildfires in north Ontario and Quebec covers the skyline in Kingston, Ontario, Canada, on June 29, 2023. Smoke from Canada's worst-ever wildfires was severely impacting air quality June 28, 2023, across Ontario and at least 15 US states, with monitors warning that over one hundred million people face potentially unhealthy conditions. The wildfires, the largest ever recorded in Canada, have raged for two months.
A blanket of smoke from wildfires in northern Ontario and Quebec covers the skyline in Kingston, Ontario, Canada, on June 29. Photo: Lars Hagberg/AFP via Getty Images
A screenshot of a tweet by Copernicus EU showing a map of wildfire smoke over the European island of Sardinia, saying:  " Hundreds of #wildfires continue to rage across Canada🇨🇦, producing huge clouds of smoke☁️ which are traveling all the way to Europe  ⬇️As shown in this #Copernicus #Sentinel3🇪🇺🛰️image, on 28 June, the smoke had reached #Sardegna🇮🇹  after travelling thousands of km."
Photo: Copernicus EU/Twitter
The Toronto skyline is seen covered by smoke from the CN Tower as wildfires in northeastern Ontario and Quebec continue to burn, in Toronto, Canada on June 28, 2023. Toronto claimed one of the top spots on a list of the world's worst air quality on Wednesday, according to global air quality tracker IQAir. Environment Canada has issued a statement for the City of Toronto due to wildfire smoke.
The Toronto, Canada, skyline is seen covered by smoke from the CN Tower as wildfires in northeastern Ontario and Quebec continue to burn on June 28. Photo: Arif Balkan/NurPhoto via Getty Images

More from Axios:

Editor's note: This article has been updated with more images.

Go deeper