Image source, Getty Images

As we close our live coverage today, the US northeast continues to wither under oppressive smoke.

• New York City is still dealing with some of the worst air quality the city has recorded in recent history, but it has improved since Wednesday
• Residents in other cities, like Philadelphia, Washington DC and even Chicago and Boston, are being told to remain inside as the foul weather continues into the weekend
• Canadian firefighters are continuing to battle blazes in eastern Canada, and have received help from the US and other countries including France, Spain, New Zealand, Australia and South Africa
• The smoke has caused flight delays and travel disruptions across eastern North America
• Parks and playgrounds are closed in Washington DC and residents across the northeast have been warned to remain indoors due to unhealthy air conditions

Today's page was brought to you by Juan Benn, Chelsea Bailey, Madeline Halpert, Mike Wendling, Max Matza and Jude Sheerin and was edited by Nathan Williams, Brandon Livesay and Marianna Brady.

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Millions advised to mask up due to intense smoke

Georgina Rannard
Climate and science reporter

It’s come as a surprise to many that New York and nearby US cities are so badly affected by Canada’s fires.

But the smoke is also reaching Europe, says Albert Ansmann at the Leibniz Institute for Tropospheric Research.

He and his colleagues can detect the particles with laser instruments pointed upwards that measure smoke-reflected light.

Hot air over a forest fire causes the smoke to rise by 2.7km, and when it absorbs sunlight, it can ascend to 10-12km height, Dr Ansmann explains.

Smoke from the North American fire season has travelled to Europe’s skies almost every summer for the past 10 years. It travels on winds from west to east for several weeks to months. The smoke particles stay in the air until they get washed out by rain or clouds.

It usually remains in the stratosphere for a few weeks but the concentration decreases over time as it spreads further out.

After the large Canadian fires in 2017, smoke was detected in the stratosphere for more than half a year afterwards.

But the record-breaking size of the fires this year means there is much more smoke in the air, pushing more smoke around the globe, Dr Ansmann explains.

This video was taken from across the Potomac River. From this view, the Jefferson Memorial in Washington DC would typically be quite clear.

Crews in Canada are still battling more than 400 blazes that have displaced 20,000 people nationwide.

Image source, EPA

Image source, EPA

The pall of drifting smoke has brought another day of hazy skies hundreds of miles to the south in the US.

Image source, Getty Images

Image source, Getty Images

Image source, Getty Images

Image source, Getty Images

Image source, Getty Images

Image source, Getty Images

For the second day in a row, outdoor events are being cancelled in Canada and across the US east coast.

• A number of large school districts including Newark and Elizabeth in New Jersey and Yonkers, just north of New York City, cancelled classes.
• Outdoor activities in Toronto have been cancelled or will be moved inside, city officials said.
• New York City pupils had a pre-planned day off today, but other districts in the area moved to remote learning or reduced their schedules.
• Outdoor school events and class trips were cancelled in Philadelphia, and other school districts across the region followed suit.
• The National Zoo in Washington is usually open every day except for Christmas – but is closed today because of the smoke.
• The Washington Nationals baseball team have rescheduled today's game against the Arizona Diamondbacks until 22 June.

Image source, Getty Images

US President Joe Biden has given an update on the smoke and fires situation.

He says that since May, more than 600 US firefighters have been deployed to help put out the blazes alongside Canadian firefighters.

He called the fires "another stark reminder of the impacts of climate change", adding it was likely to be the worst fire season in Canada's history.

Biden said he spoke with Canadian Prime Minister Justin Trudeau yesterday and offered additional support to put out the fires, particularly those in Quebec.

He said the National Interagency Fire Center would respond quickly to Canadian requests for more firefighters and fire suppression tools such as air tankers.

Image source, Getty Images

It's 14:15 here on the east coast of the US and air pollution levels are still dangerous in multiple areas.

Here's what some US cities are experiencing:

1. Washington, DC, with a "very unhealthy" air quality index of 236
2. Philadelphia, Pennsylvania, with a "very unhealthy" air quality index of 163
3. New York City, with a "very unhealthy" air quality index of 132
4. Chicago, Illinois, with an "unhealthy" air quality index of 123
5. Detroit, Michigan, with a "poor" air quality index of 79

Officials in several major cities have said the smoke should start to subside tomorrow and conditions will get better into the weekend.

Franz Strasser
US reporter

Washington DC's air quality index is currently 236, which the EPA considers "very unhealthy".

It reached close to 300 earlier, so it is worth taking a historical look at daily air pollution charts for the US capital.

Since the turn of the century the city has had only four days marked as red, with an AQI between 151 and 200. Not a single day was purple, indicating a level of 200 and above.

That streak will be broken today.

(This excludes the annual July 4th fireworks to mark Independence Day, which spikes the AQI).

Image source, EPA

The number of days when sensitive groups had to be concerned has actually trended down in recent years.

Records from the past decade show only 1-2 days out of the year had AQI levels over 100.

Image source, EPA

Juan Benn Jr, reporting from Baltimore

Lunch has arrived in downtown Baltimore and queues are forming at the Pratt Street Market, an open air food hall.

Here, the smoke from the wildfires mixes with the smell from the charcoal grill at the Soul Smoke BBQ stand.

There aren’t many people wearing masks, but perhaps that’s because they’re more concerned with eating their lunch.

Sean Montague set up his stall today and he’s selling his handmade shirts commemorating black history. He said initially he was concerned that the market would be closed today but decided to wear a mask and come out.

Normally, “there would be even more people in the downtown area,” he said.

“But you have to put your health first and be cautious.”

Image source, Getty Images

It's pride weekend in many cities and towns across the country, and organizers will soon have to make decisions on if to go forward with outdoor events as planned.

An event celebrating Pride Month on the South Lawn of the White House was rescheduled from this afternoon to Saturday because of the poor air quality in Washington DC.

On Saturday, in major cities on the east coast, several events are planned, including the DC Pride Parade, the Brooklyn Pride Festival and the Philly Pride Parade and Festival.

Event coordinators have not yet commented on whether the planned festivities will still take place.

Juan Benn Jr, reporting from Baltimore

James and his three dogs were on their regular morning walk, when we ran into him on our way to the inner harbour in Baltimore, Maryland.

Baltimore is about an hour away from the US capital, Washington DC, and is experiencing unhealthy levels of air quality today.

James described the walk as normal and not “inconvenient”, despite having to wear a mask due to the smoke lingering in the air.

James said that his dogs did not appear to be “heavily affected”.

However, depending on how the dogs react to the environment, James said he’ll shorten their time outside.

Image source, Getty Images

Washington DC Mayor Muriel Bowser shared an update with the public on Thursday, announcing closures of city parks, fields and playgrounds.

In DC, air quality remains "very unhealthy", according to local advisories.

"The basics of it is: If you don't have to be outside, then don't be outside," Mayor Bowser said. "And if you do need to be outside, then wear a mask and limit your exposure."

Bowser said the city would stop trash and recycling pickups on Friday out of an abundance of caution.

Officials said they expected the situation to improve by late Friday or early Saturday. They added that the city was not seeing an uptick in hospital visits due to the smoke.

Have you been affected by the wildfires or air quality? What precautions are you taking?

Click here to get in touch. Scroll to the form at the end of the article to tell your story to the BBC.

Image source, Getty Images

Zoos across the east coast are shut down today due to the hazardous air conditions.

In New York, the Bronx Zoo, Central Park Zoo, Queens Zoo and Prospect Park Zoo will be closed today. The facilities were closed on Wednesday too, when animals were brought inside for their safety.

In Washington DC, where air quality has reached hazardous levels, the Smithsonian’s National Zoo will not open today.

The zoo says the closure is for “the safety of our animals, our staff and our guests”.

Image source, Getty Images

New York Mayor Eric Adams held a news conference earlier this morning where he answered questions from reporters about the ongoing poor air quality situation.

He said there was a chance for "significant improvement" by tomorrow morning and throughout the day on Friday since no more large plumes are expected based on the current smoke forecast.

But he cautioned that a sea breeze this afternoon could "push smoke back over the city".

New York officials have told residents to avoid going outside as much as possible as the city ranks number one among major metropolitan areas around the world for the worst air pollution today.

Image source, Getty Images

Today's Major League Baseball game between the Washington Nationals and the Arizona Diamondbacks has just been called off because of the poor air quality in Washington DC. It will now be played on 22 June.

It comes after the New York Yankees had to reschedule Wednesday's game for the same reason.

In the New York borough of Queens, the first day of the three-day Belmont Stakes Racing Festival in Elmont was canceled today because of poor air quality conditions.

New York City is also hosting the annual Governor's Ball musical festival this weekend, which starts tomorrow. As of now, it's still on. But organisers said they were "closely monitoring" the smoke situation.

Several Broadway shows, including Hamilton, were cancelled on Wednesday after cast members called in sick.

Juan Benn Jr, reporting from Baltimore

We’ve just arrived in Baltimore, Maryland. Coming into the city, the whole skyline was washed out in gray smoke.

I’m from East Tennessee, and the sight reminded me of the bluish-gray haze that gives the Great Smokey Mountains their name. The current air quality here is 190. According to researchers at Stanford, an AQI of that level is equivalent to smoking almost 10 cigarettes a day.

Chelsea Bailey and I will be bringing you updates from the city throughout the day, so stay tuned.

Cities in North America have the worst air quality in the world today.

Here's where things stand as of 11:15 ET (16:15 BST) on the US Enviornmental Protection Agency's Air Quality Index (AQI, external).

• Washington DC - 293
• Philadelphia - 270
• New York City - 199
• Balitmore - 190

The city of Harrisburg in Pennsylvania is currently at 380 on the AQI.

In comparison, here are some of the worst cities on the AQI outside of North America.

• Lahore - 161
• Dhaka - 154
• Hanoi - 152

• Abu Dhabi - 121

In Canada, Toronto has an AQI of 75. But there are areas with very high levels, such as Janvier in Alberta, which currently has an AQI of 338.

A reminder that anything between 201-300 on the AQI scale is deemed "very unhealthy" and above 301 is "hazardous".

Countries around the world are sending hundreds of trained specialists to help put out the wildfires.

• The US is sending 600 firefighters, White House Press Secretary Karine Jean-Pierre said during a daily briefing yesterday. They include a crew making a 1,000-mile (1,600km) trek from Alaska to Alberta, external.
• EU nations including France, Portugal and Spain have offered 280 firefighters, and “more will come”, according to European Commission head Ursula von der Leyen.
• Australia and New Zealand sent 200 firefighters last month, external, with more from those countries also on the way.
• And 200 firefighters from South Africa landed in Canada last weekend - and held an impromptu singalong in Edmonton airport before heading off to tackle the fires.

Geeta Pandey
Reporting from Delhi, India

Image source, Getty Images

Images of the Statue of Liberty in New York - obscured by a thick haze of smoke caused by wildfires in Canada - have shocked the United States.

But in the Indian capital Delhi, the iconic India Gate hidden behind a layer of smog is a reality every winter.

The air gets hazardous, with pollution reaching levels nearly five times what the World Health Organization considers safe.

Residents are asked to stay inside, keep the windows and doors closed and wear masks when stepping out.

It is like a scene from a dystopian novel or an apocalyptic film, except that it is real.

Those who can afford it rush to buy expensive air purifiers. But these only work in closed rooms.

Experts say exposure to such high levels of pollution make people more prone to all kinds of infections. They can elevate the risk of heart attacks and damage vital organs like the liver and brain.

Experts say cleaning up the air requires drastic measures - but they are not a top priority for the country's leaders.

You can read more about how Delhi deals with pollution here.