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Amid record heat, dry air and strong winds, the destructive wildfire in Fort McMurray, Alberta has grown nine times larger during the course of this week. As of Friday morning, it had burned an area larger than the city of Chicago, and was still burning out of control. 

The fire grew from 29 square miles on Tuesday to at least 386 square miles. The city of Chicago is 234 square miles. Having exceeded the area of Chicago, as well as New York City, the fire is now more on par with the area of Dallas.

On Friday, a convoy of evacuees began the long drive out of oil industry work camps north of the fire-ravaged Fort McMurray area Friday morning. 

They were destined for areas south of the city, and had to pass through the fire-ravaged parts of the city in order to make the transit. 

This process of southbound convoys is expected to take four days, according to local authorities in Canada.

Meanwhile, a mass airlift of evacuees was expected to resume, a day after 8,000 people were flown out.

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About 25,000 evacuees moved north in the hours after Tuesday's mandatory evacuation, where oil sands work camps that usually house employees were used to house evacuees. 

But the bulk of the evacuees fled south to Edmonton and elsewhere, and officials are moving everyone south where they can get better support services.

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In all, more than 80,000 people have left Fort McMurray, in the heart of Canada's oil sands, and officials say no deaths or injuries related to the fire have been reported.

The Alberta provincial government, which declared a state of emergency, said more than 1,100 firefighters, 145 helicopters, 138 pieces of heavy equipment and 22 air tankers were fighting the fire, but Chad Morrison, Alberta's manager of wildfire prevention, said rain is needed.

"Let me be clear: air tankers are not going to stop this fire," Morrison said. 

Evacuee Update - May 6, 9:25 a.m. #ymmfire pic.twitter.com/hDDzRfEhVc

— RMWB (@RMWoodBuffalo) May 6, 2016

"It is going to continue to push through these dry conditions until we actually get some significant rain."

The insurance company Aon Benfield estimates this disaster will cost Canada at least $1 billion, due to a combination of fire damage, the shut down of several oil production facilities and cessation of economic activity in Fort McMurray. 

"... It is expected that once assessments are finalized, the Horse Creek Fire in FortMcMurray will end as one of the costliest natural disasters in Canada’s history," the company stated in a preliminary analysis. 

The costliest disaster in Canadian history occurred in 2013, when major floods hit Calgary, causing $1.65 billion in damage.

Environment Canada forecast a 40 percent chance of showers in the area on Sunday and Monday, along with cooler temperatures thereafter. 

However, until then, the region will still have to endure unusually mild conditions, relatively strong winds and dry air. The forecast high temperature on Saturday of 27 degrees Celsius, or 80 degrees Fahrenheit, is about 30 degrees Fahrenheit above average for this time of year. 

One by one thousands evacuated #FortMcMurray #FortMacFire #ymmfire by @RCMPAlberta @CTVNews pic.twitter.com/q3TsxP5y0k

— Peter Akman (@PeterAkmanCTV) May 6, 2016

The heat has come courtesy of a wavy flow in the jet stream known as an Omega block, so-named due to the jet stream's resemblance to the Greek letter Omega. 

The flow of air at upper levels of the atmosphere has allowed mild air to surge northward into northern Alberta, and locked in the hot and dry conditions for an entire week. 

An El Niño event in the tropical Pacific Ocean contributed to a milder- and drier-than-average winter in Alberta, which has led to an anemic snow cover throughout northwest Canada. The snow that did fall vanished from the ground unusually early this spring, though this has been a trend seen throughout the high latitudes during the past few decades.

In addition, long-term trends associated with human-caused global warming include earlier spring snow melt and later starts to the winter season, which is lengthening wildfire seasons from Alaska to Alberta, and south to New Mexico.

For example, the area burned by wildfires in Alberta has more than doubled since 1970.

Climate data shows that Fort McMurray has seen an increase in the number of days with high temperatures above 25 degrees Celsius, or 77 degrees Fahrenheit, since 1950. This number has jumped from an average of 21 such days in 1950 to an average of 35 such days in 2010.

A study published in the Proceedings of the National Academy of Sciencesin 2013 found that boreal forests, which form a ring around the world just below the Arctic Circle, have been burning at rates that are unprecedented in 10,000 years. That study tied such burn rates to warming temperatures and increased evaporation.

Global warming is also leading to more extreme fire weather days such as what occurred on Tuesday and Wednesday, with dry soils, record temperatures and strong winds. 

Additional reporting by the Associated Press.

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