(Bloomberg) -- Wildfires continue to ravage large tracts of forest in Canada, with little sign weather will provide much help to firefighters who are battling the blazes that sent smoke more than 1,000 miles southward and prompted air hazard alerts in cities on both sides of the US border.

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 was living through its “worst wildfire season” in recorded history during a briefing with journalists in Ottawa on Wednesday. 

Trudeau and President Joe Biden spoke about the fires in a call on Wednesday, according to statements from their offices. 

Biden, the White House said, had “directed his team to deploy all available federal firefighting assets that can rapidly assist in suppressing fires” affecting Canadian and US communities.

The prime minister’s office said “both leaders acknowledged the need to work together to address the devastating impacts of climate change.”

New York came to a near standstill on Wednesday in the face of what local officials called an “unprecedented event” as hazy skies turned an eerie orange. 

“This is not the day to train for a marathon or to do an outside event for your children,” Mayor Eric Adams said at a press conference, urging people to remain indoors or don N95 masks.  

Read More: World’s Worst Air Cloaks New York City in Smoky Orange Haze

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. 

Read More on Wildfire Smoke: How Wildfire Smoke Impacts Human HealthMaps and Apps Help Track Wildfire Smoke by City and Neighborhood Wildfire’s Toxic Legacy Leaves Children Gasping for Air Years Later

Ottawa, Canada’s capital, was shrouded in smoke again, and its air quality health index was rated 10+ or “very high risk” by the country’s weather agency. Sports events were canceled and officials warned older people and young children to avoid strenuous outdoor activity. Flights were still leaving Ottawa’s airport, but with a number of delays. 

“People across the country are being affected,” Trudeau said about the air quality. “We’re seeing vulnerable people at risk, outdoor events canceled, kids having to be kept inside at recess.” 

Quebec is the source of fires that are responsible for the pollution over New York. The province is facing 150 active wildfires, according to the website of a Quebec organization that tracks fire activity. 

The weather forecast gives cause for concern, as heavier rain isn’t expected until early next week in the northern part of the province and a low pressure system funnels Quebec smoke into the US.

“I want us all to be realistic and not put on rose-colored glasses,” Quebec Premier François Legault said in a press conference. More than 15,000 people in the province alone could be under evacuation orders in the next few hours.

So far, the effect on businesses in eastern Canada has mostly been limited to the mining sector. Because of a railway disruption in northern Quebec, Iron Ore Co. of Canada has reduced operations and Champion Iron Ltd expects material delays in sales of its iron ore. 

Other companies have temporarily suspended exploration activities. An emergency order from the provincial government prohibits access to lands impacted by forest fires. 

--With assistance from Brian Platt and Laura Dhillon Kane.

(Updates with Biden, Trudeau call, starting in third paragraph.)

©2023 Bloomberg L.P.