"It should help our crews out there quite a bit after a couple of really hot, really dry days when they’ve had to really work out there," he said. "Now we can try and dig in and make a little progress here." There are more than 700 firefighters working in and around Fort McMurray to contain the fire, Fairweather said.

While cooler temperatures present responders with a "great opportunity" over the next three to four days, fires deep into the forest will likely last for months, Morrison said. The fire that began a week ago probably had a human cause, though that remains unknown, he said.

‘This beast’

“This beast is an extraordinarily difficult problem,” federal Public Safety Minister Ralph Goodale told reporters Sunday, in a reference to how the fire has been nicknamed. “Because of the weather in the last few hours and the weather forecast going forward, it would appear that the situation is moderating, perhaps a bit.”

Disruptions to oil production, the lifeblood of Alberta’s economy, add to a human catastrophe as blazes razed entire neighborhoods in Fort McMurray, the gateway to the world’s third-largest crude reserves. All of the 25,000 people who had gone north to flee the fire have been evacuated south and the majority of them are in Edmonton, Notley said.

The wildfires covering an area twice the size of New York city have led to production cuts of about 40% of the region’s output of 2.5 million barrels, based on IHS Energy estimates. The cuts, and the mass exodus from Fort McMurray, are another blow to an economy already mired in recession from the oil price collapse.

West Texas Intermediate for June delivery fell 1.7% to $44.93 a barrel at 11:11 a.m. on the New York Mercantile Exchange.

Syncrude operations

Once the fires are under control, oil-sands-mining projects could be back to normal production levels in about a week, Morgan Stanley said in an e-mailed research note on Monday. In-situ projects, which use steam to extract the oil, could take two or more weeks depending on the start-up method and pressure requirements, it said.

Related: 10 most costly wildland fires in the U.S.

Syncrude Canada, a joint venture controlled by Suncor, shut down its Aurora mine and Mildred Lake operation about 40 kilometers north of the city and has evacuated about 1,200 workers. Syncrude has a capacity for 350,000 barrels of oil a day. Morrison said the oil facilities are highly resistant to fire with their buffer zones.

Smoke reached Syncrude’s Mildred Lake site Saturday, company spokesman Leithan Slade said in an e-mailed statement. “We will bring operations back online only when it is safe to do so.”

Oil sands and the environment: Quick take

Suncor, Phillips 66 and Statoil ASA have declared force majeure — a provision protecting companies from liability for contracts that go unfulfilled for reasons beyond their control — on supplies from the region. As the fires are set to move away from its oil-sands operations, Suncor said it has begun planning the restart of production after moving more than 10,000 employees, families and Fort McMurray residents out of the region. The restart will happen once it’s safe and when third-party pipelines are available, the Calgary-based producer said.

Husky Energy Inc., controlled by Hong Kong billionaire Li Ka-Shing, said Sunday it has completely shut its Sunrise facility, which has a capacity of 60,000 barrels a day and was producing about half that before the blaze began. Nexen’s operation, with a capacity of 92,000 barrels a day, was shut. Phone and e-mail messages left for Colleen Brown, a Nexen spokeswoman, seeking comment on damage to the facilities weren’t immediately returned.

The inferno around Fort McMurray may become the costliest catastrophe in the country’s history with insurance losses potentially reaching C$9.4 billion ($7.3 billion) if all homes in the city are lost. Bank of Montreal cut its second-quarter gross domestic product growth estimate to zero from 1.5%, citing “severe disruptions to oil production” due to the fires. BMO said the estimate was a placeholder, dependent on receiving more information on the scope of the disaster.

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