The Philadelphia region faced the worst air quality in the US early Thursday as the impact of Canadian wildfires continued to ripple south.

Large swaths of the Northeast and Mid-Atlantic experienced unhealthy levels of pollution, while the National Weather Service warned of deteriorating conditions into Alabama and Georgia. The impact could last for several days.

President Joe Biden offered additional support to fight the blazes, as the effects of the smoke blanketed some cities with an apocalyptic tinge, forcing officials to urge residents to stay indoors. New York state planned to distribute a million N95 masks on Thursday. The Federal Aviation Administration continued to report flight delays due to low visibility.

Canadian Prime Minister Justin Trudeau has said the country is living through its “worst wildfire season” in recorded history, with more than 400 blazes across the country.

Key Stories:

• Choking New Yorkers Get Little Solace From Wildfires Overseas
• Out of Control Fires Rage in Canada, Smoke Covers US Skies
• NYC Flights Delayed as Wildfire Smoke Blankets the Region
• Canada Wildfires Envelop Millions of North Americans in Smoke
• Big Take: Wildfire Smoke Leaves Children Gasping for Air Years Later

Here’s the latest news: (All times are NY)

‘Hazardous’ Conditions in Philadelphia (3:51 a.m.)

“Hazardous” air lingered over Philadelphia early Thursday, according to the National Weather Service’s interactive map. New York continued to see “Unhealthy” to “Very Unhealthy” air quality, while the situation in the Washington, D.C. area was “Unhealthy.”

At Unhealthy levels, people who are active outdoors may start to experience some respiratory effects, according to the Environmental Protection Agency’s Air Quality Index. Hazardous conditions trigger emergency conditions.

Air Quality to Decrease in South (3:32 a.m. Thursday)

The National Weather Service has issued Air Quality Alerts for parts of the Great Lakes and Ohio Valley to the Northeast and Mid-Atlantic, it said in a statement. The impact of the fires has spread into the South, with the air quality in Alabama and Georgia set to decrease on Thursday.

Biden, Trudeau Speak (10:10 p.m. Wednesday)

President Joe Biden offered additional support to fight the wildfires burning in Canada during a call with Prime Minister Justin Trudeau, according to a readout of the conversation. The US has already deployed more than 600 firefighters and support personnel, and Biden directed his team to provide all available assets that can rapidly assist in suppressing the blazes.

Trudeau Says Climate Change to Blame (7:21 p.m.)

Trudeau made the comment after the call with President Biden. He added that hundreds of US firefighters have arrived in Canada, and more are on the way.

New York to Distribute N95 Masks (5:31 p.m)

Wildfires Burn in Canada’s Worst Season (4:30 p.m.)

Wildfires continue to burn large tracts of forest in Canada, with little sign weather will provide much help to firefighters who are battling the blazes that are sending smoke over New York and other major cities.

More than 400 forest fires are still active across the country, and most of them are out of control. Prime Minister Justin Trudeau said Canada is living through its “worst wildfire season” in recorded history during a briefing with journalists in Ottawa on Wednesday.

Wildfires are poised to burn more land than ever in Canada, with over 3.8 million hectares (9.4 million acres) scorched so far, according to the Canadian National Fire Database. That’s about double the size of New Jersey.