Tens of millions of Americans awoke to hazy skies on Thursday morning as smoke blowing in from climate change-fuelled wildfires in Canada continued to hang over the north-eastern US and the mid-Atlantic region.
“This morning, millions of Americans are experiencing the effects of smoke resulting from devastating wildfires burning in Canada – another stark reminder of the impacts of climate change,” US President Joe Biden said in a statement.
The National Weather Service (NWS) said “hazardous” air hung over Philadelphia early on Thursday. New York, where the skyline was barely visible on Wednesday, continued to experience air quality classified as “unhealthy” and “very unhealthy”. Meanwhile, “unhealthy” air persisted in Washington.
With Canada set to experience its worst wildfire season on record, UN Secretary General Antonio Guterres has called for more action to reduce the risk of fires.
“At our UN headquarters in New York, we can feel the deteriorating air quality as smoke from the wildfires in Canada moves south,” he said in a tweet.
“With global temperatures on the rise, the need to urgently reduce wildfire risk is critical. We must make peace with nature. We cannot give up.”
The hazy conditions over New York were so extreme on Wednesday that the two cities briefly overtook New Delhi in a list of the world's most polluted cities, according to the IQAir quality and pollution city ranking.
The index measures levels of the fine-particulate PM2.5, which can enter the respiratory tract and lungs. This, in turn, can irritate conditions such as asthma and even cause heart issues over the long term.
It is an unusual turn of events, because in the 2022 World Air Quality index from the same monitor, the US had the 99th worst air quality compared with 131 other nations. Wildfires are the biggest contributor to poor air quality scores in the US.
The NWS also set air-quality alerts for parts of the Great Lakes and Ohio Valley regions. Air quality in Alabama and Georgia were also predicted to deteriorate on Thursday.
Washington resident Asher Huey said he opened his front door on Wednesday to the pungent smell of smoke reminiscent of “a campfire”.
Mr Huey said his mother, who is from New York, woke up with a sore throat from the poor air quality. He told The National she thought she had Covid.
A test quickly revealed that the virus was not the culprit.
The poor air quality did not deter Sam Burton from going for a morning run, but it reminded her of her home state of Utah, which has long suffered from poor air quality due to western wildfires.
“It totally concerns me,” said Ms Burton. “It's such a scary thing and in fact, I think because of where I grew up, it's more concerning because you see it every year there.”
Trent Ford, the state climatologist in Illinois, said the atmospheric conditions in the upper Midwest creating dry, warm weather made it possible for small particulates to travel hundreds of kilometres from the Canadian wildfires and linger for days.
“It’s a good example of how complex the climate system is but also how connected it is,” Mr Ford told the Associated Press.
An air quality health advisory has been issued for all five New York boroughs through Thursday, New York City Mayor Eric Adams said.
“This is an unprecedented event in our city and New Yorkers must take precaution,” he said at a briefing on Wednesday. He added that people “should limit outdoor activity to the greatest extent possible”.
City and state officials advised people to keep their windows closed and use air purifiers. They also said that people at risk of asthma, heart or breathing problems should wear high-quality masks if they must go outside.
New York City-area airports suffered lengthy delays due to low visibility with the smog, and LaGuardia International Airport underwent a brief ground stop on Wednesday.
In New York and Washington, schools told parents that pupils would remain indoors and outdoor activities were cancelled.
“Many staff and parents are concerned about the wildfires in Canada and the resulting poor air quality that we are experiencing here,” said the administrator of a school in the Washington neighbourhood of Chevy Chase.
Canada is expected to mark its worst wildfire season since records began if current trends continue.
The White House said the US is sending hundreds of firefighters to support firefighting efforts.
Canadian Prime Minister Justin Trudeau tweeted: “On the phone today, I spoke with [US President Joe] Biden about this critical support – and I thanked him for all the help Americans are providing.”
Towns in Quebec have been evacuated and some of the country's lucrative mining operations closed as the fires rage.
“We are not expecting rain in the short term, which is what makes it more difficult to fight fires,” Ms Blanchette Vezina said.
Quebec Natural Resources Minister Maite Blanchette Vezina said in Quebec City that evacuees across the province number a little more than 8,300, down from 10,000 at the start of the week.
“We’re seeing more and more of these fires because of climate change,” Mr Trudeau said in a tweet.
“These fires are affecting everyday routines, lives and livelihoods, and our air quality. We’ll keep working – here at home and with partners around the world – to tackle climate change and address its impacts.”
Many experts say the extreme weather and wildfires are fuelled by climate change.
The climate crisis is causing abnormal levels of heat and drought. It is also intensifying wildfire seasons, leading them to start earlier, last longer and have fiercer impacts.
Climate change is also causing a decline in air quality due to pollution and smog events like wildfires. Air pollution is behind at least seven million premature deaths annually, the World Health Organisation says.
“This may be the first time we've experienced something like this on magnitude. Let's be clear, it's not the last,” Mr Adams said.
“Climate change is accelerating these conditions.”