Image source, Getty Images

Flight disruptions continue this morning as the wildfire smoke worsens visibility in North America.

The Federal Aviation Administration has now delayed all flights bound for New Jersey's Newark Airport.

Earlier this morning, the agency paused flights from the Northeast, Mid-Atlantic an Ohio bound for Philadelphia International Airport as well as New York's LaGuardia Airport because of low visibility.

If you are flying today you can check the latest on delays here., external

The BBC's weather team explains when we can expect the toxic smoke to dissipate.

Wildfire smoke will reach as far south as Florida, but the worst of it will stay in the north east of the US and across Canada.

The forecast shows smoke will linger until the weekend.

Click the play button above to see which areas will have the worst air quality.

Forest fires are continuing to blaze across Canada today.

So far, nearly 4m hectares of land has been burned.

Quebec was hit with some of the worst fires, with thousands of people forced to evacuate their homes.

As of Thursday morning, more than 400 fires were burning across Canada, including 236 that were out of control, according to the Canadian Interagency Forest Fire Centre.

Wildfire smoke is spreading across much of the country and is set to worsen in the province of Ottawa and in Toronto.

You can see the forecast for drifting smoke here.

Georgina Rannard
Climate and science reporter

Scientists say climate change has likely made the dry and hot conditions fuelling these wildfires in Canada worse.

But there’s another phenomenon that could make next season even worse - called El Niño.

It’s the world’s most impactful weather event, linked to the pattern of winds blowing above the Pacific Ocean.

They reduce cold water coming from the depths of the ocean to the surface. Warmer water then stays close to the surface and spreads further. This releases more heat into the atmosphere, creating wetter and warmer air.

El Niño occurs every 2-7 years. It tends to make Canada hotter and drier than usual, external, and was behind a serious drought in 2014-16.

Scientists in the US have just confirmed that the El Niño pattern has started again.

It is expected to last until next spring, bringing serious weather impacts later in 2023 and next year.

Scientists say it will probably make 2024 the hottest year on record and is likely to drive a powerful wildfire season.

The strongest impacts on wildfires will probably be in Australia, but as it will drive up temperatures globally, the effects will be felt around the world, including in Canada.

Image source, Getty Images

Millions of people in major US East Coast cities and Canada are waking up this morning to health advisories.

In New York, Philadelphia and Washington, DC, officials are advising residents to stay inside and wear a well-fitting mask when venturing outdoors.

Vulnerable populations - including the elderly, young children and the immunocompromised - are advised to avoid going outside as much as possible.

In Canada, residents in parts of Alberta, where wildfires are raging, and Ottawa are under health alerts.

The smog is affecting other parts of the US, too, including the Midwestern states of Michigan and Ohio.

Canada's wildfire smoke has impacted air travel due to reduced visivility.

As of 08:30 ET, departures at Philadelphia International Airport are grounded.

At New York's La Guardia Airport, departures are delayed on average 54 minutes and there are general ground delays.

The Federal Aviation Administration tweeted there will continue to be delays throughout the day.

"We will likely need to take steps to manage the flow of traffic safely into New York City, DC, Philadelphia and Charlotte," the tweet reads.

If you are flying today you can check the latest on delays here., external

The thick smoke continues to hang over major cities in North America, so let's take a look at how bad the air quality is.

We are using the Air Quality Index (AQI) which indicates how clean or polluted the air is around you. The index runs from 0-500 and the higher the number, the worse it is for your health.

Anything from 151-200 is designated as "unhealthy". When the number is between 201-300 it's "very unhealthy" and the the risk is increased for everyone. The highest level is "hazardous" and occurs when the AQI is above 301.

These are the AQI levels in a handful of US east coast cities as of 07:30 local time (12:30 BST).

• Philadelphia - 369
• Washington DC - 235
• New York City -222
• Buffalo - 131

Image source, Reuters

• Millions of people across North America have been advised to wear N95 (high-grade) masks outdoors - due to air pollution created by intense wildfires in Canada
• Nearly 100 million people are experiencing poor air quality across the continent, according to the Canadian government
• Much of the smoke is coming from Quebec, where 150 fires are burning in what is already the Canadian province’s worst wildfire season on record. The US has sent firefighters to help
• New York City and Ottawa with “hazardous” air yesterday. The issue caused Killing Eve star Jodie Comer to walk off stage during a Broadway show
• The dangerous conditions are expected to last into the weekend

Nathan Williams
Live reporter

Hello and welcome. We're restarting our live coverage as intense wildfires in Canada continue to hit the air quality for millions in the eastern US and Canada.

People are being advised to wear high-grade masks outdoors, and in New York, authorities will begin to give out millions of free masks today.

I'm here with my colleagues Sam Hancock, James FitzGerald and Nicholas Yong to bring you the latest.

As we close our live coverage, the air quality in Ottawa appears to be improving while it remains steadily hazardous in New York and the surrounding area.

Today's page was brought to you by Sam Cabral, Nadine Yousif, Juan Benn, Mike Wendling, Chloe Kim, Max Matza and edited by Brandon Livesay and Marianna Brady.

You can read the latest on the air quality story here.

People across the eastern US and Canada are bracing for an evening indoors as the air quality remains unhealthy and in some places, hazardous.

Here are some of the latest pictures.

Image source, Getty Images

Image source, Getty Images

Image source, Getty Images

There are more than 20,000 people currently evacuated from their homes due to wildfires across Canada.

Around 11,400 of those people live in remote parts of northern Quebec. Another 4,000 are expected to evacuate soon as the fires rapidly spread.

The fires have been significantly felt by indigenous communities. On Tuesday night, Oujé-Bougoumou, a Cree community located about 750 kilometres north of Montreal, was one of several that was ordered to evacuate immediately.

As people left their homes, a long line of vehicles standing bumper to bumper dotted the only highway out of town.

"What normally takes two hours... some reported taking about six hours. Some were driving all night," former Grand Chief Abel Bosum of Oujé-Bougoumou told the CBC., external

Other communities badly affected by wildfire smoke also began evacuating vulnerable people on Wednesday.

Quebec's premier Francois Legault said it is likely that people won't be able to return to their homes until next week, as dry weather in the province is forecasted to persist into the weekend.

Explained, in 80 seconds...

Hundreds of outdoor events have been called off today throughout the eastern US and Canada:

• The New York City Parks Department canceled outdoor events and closed city beaches
• School activities up and down the east coast - including sports games and practices, field trips and outdoor recesses were cancelled, according to Reuters and local reports
• Horse races were cancelled at several tracks in the region
• Major League Baseball games have been called off in New York and Philadelphia

If you're in a smoke affected area, here's some advice on how to stay safe.

We spoke to Dr Susan O’Mara, chair of the Department of Emergency Medicine at Medstar Washington Hospital Center in Washington DC.

• Smoke inhalation causes inflammation in the lungs, threatening the small airways, she explains
• Anyone with asthma or chronic obstructive pulmonary disease (COPD) should stay indoors, to reduce swelling of the airways. “This is the time to be taking all your medicines as directed and on time”
• Symptoms of smoke inhalation include wheezing, coughing, runny nose and eyes. Seek medical attention if you begin to feel short of breath
• Staying indoors and utilizing air purifiers and conditioners are the most helpful measures as the air quality remains poor
• If you must go outside, wear an N95 mask. Surgical, cloth and gator masks don't protect you from small particles, but an N95 will
• Limit outdoor activity to only what's necessary - no strenuous excercise

Image source, Getty Images

Millions are under air quality alerts as smoke from Canadian wildfires drift into the US.

A storm system off of Nova Scotia pushed smoke south and then east, causing major northeast US cities to feel the brunt of it on Wednesday.

Places further south are likely to see more smoke tomorrow, which could reach as far south as South Carolina.

Due to weather patterns, the haze will likely persist in New York City tomorrow and Washington DC could see more smoke as well.

New York City might see some improvement in air quality by Thursday evening, but wind shifts could make conditions worse in western New York and Pennsylvania.

Image source, Getty Images

The potentially dangerous smoke blanketing North America has a beautiful, eerie side effect: it turns the sun red.

There’s a scientific explanation for this colour shift.

Clouds of small particles emerging from the wildfires and spreading across the skies absorb shorter wavelengths of light (bluer shades) and scatter longer wavelengths which come from the redder side of the spectrum.

More of that longer-wavelength light reaches our eyes and thus the sky and the sun in particular takes on a reddish hue.

The effect is particularly noticeable when the sun is closest to the horizon – at sunrise and sunset.

Robin Levinson King
Reporting from Toronto, Canada

Image source, Getty Images

In the greater Toronto area, the air is thick with the smell of campfire. But this is no summer cookout.

Winds have blown smoke from fires in the east all the way to Canada’s largest city and surrounding areas. Now millions of people are under air quality warnings, being told to stay in doors and refrain from strenuous exercise.

On a short walk for a cup of coffee, I felt my own breath heavy, the air dry and acrid. I won’t be leaving the house again anytime soon.

Although seasonal patios are a popular summertime addition during the warmer months, some businesses have decided to close them down, which will inevitably lead to economic costs as well.

Image source, Getty Images

An indoor basketball match this evening between the New York Liberty and the Minnesota Lynx WNBA teams has been postponed due to smoke, according to the league.

The game "has been postponed due to the air quality issues impacting the Barclays Center in Brooklyn and the greater New York area following the wildfires in Canada," the WNBA posted on Twitter.