FORT MCMURRAY, Alta. -- A raging forest fire whipped up by shifting winds sliced through the middle of the northern oilsands hub city of Fort McMurray on Tuesday, sending tens of thousands fleeing in both directions and prompting the evacuation of the entire community.

The blaze, which had burned since Sunday but seemed on its way to being neutralized Tuesday morning, overwhelmed firefighters when winds shifted quickly and drastically in the mid-afternoon to the southwest of the city.

Officials said flames stormed along a ravine and roared into the city and the race was on to get out.

Pictures and video on social media depicted a hellish scene of fountains of flame.

There was fire jumping roads, burning debris pitched into the paths of cars as frantic residents, lined up bumper to bumper, scrambled and fumbled to find their way through the thick grey haze.

"It became chaotic with vehicles trying to swerve and pull out into the ditch," said resident Jordan Stuffco.

Air tankers and helicopters buzzed overhead.

"(With) the heat from the oncoming smoke and the flames, you could see mini-tornadoes forming near the road. It was something out of an apocalyptic movie."

The blaze razed homes on the city's western edge, though it was unclear how many. Officials confirmed some homes in a trailer park were torched.

As the afternoon wore on and the fire intensified, more and more sections of the city were ordered evacuated until the entire community, an estimated 80,000, was ordered out after 6 p.m.

Resident Carol Christian drove to an evacuation centre with her son and cat.

"When you leave ... it's an overwhelming feeling to think that you'll never see your house again," she said, her voice breaking.

"It was absolutely horrifying when we were sitting there in traffic. You look up and then you watch all the trees candle-topping ... up the hills where you live and you're thinking, 'Oh my God. We got out just in time.' "

Highway 63, the main way into Fort McMurray from the south, was closed after flames jumped the road. Those who had headed south were told to stay away while those who couldn't head south headed north.

Alberta Premier Rachel Notley, speaking to reporters in Edmonton, said the province was doing all it could to ensure everyone's safety. She said she was looking into the possibility of an airlift for residents with medical issues.

"As frustrating and as scary as it is to leave your home, it's not as frustrating and scary as to find that you're trapped," said Notley.

"It is absolutely important that people follow instructions and evacuate as requested."

She said 160 Mounties were on scene trying to get people out.

Officials said there was no word of any injuries or people laid up by smoke inhalation.

Resident Sandra Hickey said the situation changed quite quickly.

"When I got in the shower earlier today the sky was blue. When I got out, the sky was black," said Sandra Hickey, who had to leave her home. "It was fast. The wind picked up and changed direction."

Fire officials had already warned earlier in the day that rising temperatures and low humidity could help the fire grow.

Unseasonably hot temperatures combined with dry conditions have transformed the boreal forest in much of Alberta into a tinder box. The wildfire threat ranged from very high to extreme.

Government spokesman Bruce Mayer said a cold front was expected to come through the region by mid- to late-day Wednesday, which would bring with it shifting winds gusting to 50 km/h. He said to expect "a more intense burning day."

North of Fort McMurray, work camps associated with oilsands projects were being re-purposed to house evacuees.

Notley said the camps have secured spaces for 6,000 people, "but we know we need to find more."

Fort McMurray is the capital of Alberta's oilsands region and sits about 435 kilometres northeast of Edmonton.

It was five years ago this month that wildfires destroyed about one-third of the community of Slave Lake, Alta. More than 500 homes and buildings were damaged at a cost of hundreds of millions of dollars.

Notley said the Fort McMurray situation rivals the Slave Lake catastrophe.

"In terms of fire this is our biggest fire evacuation," she said. "This is bigger than Slave Lake."

- With files from Chris Purdy, Mary-Jo Laforest, Dean Bennett and Jennifer Graham.