What to Know About Canada’s Exceptional Wildfire Season

Follow our live updates on the Canadian wildfires and air quality.

Canada is burning.

That, at least, is the perception around the world as hundreds of fires have convulsed the country, forced tens of thousands of people to flee and sounded a global alarm about the perils of climate change.

Canada’s wildfire season came early and with unusual vigor this year, bringing destruction to areas including parts of Quebec which usually escape their effects.

The disruption their smoke brought to large cities in both Canada and the United States last week has been a potent reminder of the consequences of climate change.

The skyline of New York City and other cities in the Northeast are no longer an apocalyptic orange from smoke that was dangerous to breathe last week. But in Canada on Friday, it was floating above cities as a haze, and hundreds of blazes remained out of control.

In a nation famed for its orderliness, the out-of-control fires have created the ominous feeling of a country under siege, stretching from the west to the east coasts and sending toxic plumes over major cities like Ottawa, the capital, Toronto, the largest city and financial capital, and Montreal.

Here’s what you need to know about the fires and Canada’s wildfire season.

An early start.

While wildfires are common in the spring and summer in much of Canada, they usually burn in remote and sparsely populated areas. But this year’s fires have already been remarkable: Hundreds are burning across much of the country, covering an area already larger than burned all last year.

A dry, windy and abnormally warm spring created ideal fire conditions in many regions, with the first major fires erupting last month in Alberta, an oil-and gas-producing province that is regularly plagued by blazes.

So far, more than 2,600 fires have consumed about 13 million acres of forest, far higher than the 140,000 acres that had burned by this point last year.

The fires are likely to multiply.

The Canadian government forecast shows all of the country — except the Arctic regions where trees don’t grow — at an above average risk for wildfires for the rest of June. Ontario and British Columbia have seen relatively limited fire activity, but most experts anticipate that will not last.

The distribution of the major fires is also unusual: from Alberta in the west to Nova Scotia on the Atlantic coastline, three time zones away. The smoke that plagued the United States mostly blew down from areas in Quebec that are not normally associated with major wildfires.

What is starting the blazes?

Lightning typically sets off about half of Canada’s wildfires each season. Those fires are generally the most damaging because they tend to start in remote areas and are difficult for firefighters to access. They account for about 85 percent of the forest that is burned most seasons.

Humans are to blame for the other half of the fires not caused by lightning, setting them off in a variety of ways, usually unintentionally. One of Alberta’s fires this year started when an all-terrain vehicle burst into flames. Sometimes carelessness sparks fires. As a result, some provinces have closed parks and forests to people and have banned camping and all outdoor burning to limit risk.

In past years, sparks from trains braking while descending mountain passes have also caused fires.

Is climate change involved?

Climate research suggests that heat and drought associated with global warming are major reasons for the increase and a contributor to bigger fires.

Canada has the world’s largest intact forest ecosystem, and many parts of the country have experienced drought and high heat recently. That can make trees vulnerable to fire and can dry out dead grass, pine needles and any other material on the bottom of the forest floor that can act as kindling.

Wildfire experts see the signs of climate change in the dryness, intense heat and longer fire season that have made these fires more extreme and are likely to do so in the future.

Why is firefighting capacity so badly stretched?

Canada does not have a national wildfire fighting force but relies on its 10 provinces and three territories.

In normal times, a coordination center shuffles firefighters and equipment like water bombers and helicopters from provinces with few fires to crisis areas being convulsed by blazes.

These, however, aren’t normal times.

The scope and scale of this year’s fires are making it difficult for provinces to share firefighters and equipment, and the system is stretched to the limit.

To help ease the strain, more than 5,000 firefighters have traveled to Canada from abroad, including groups from France, Chile, Costa Rica, Portugal, the United States, Australia, New Zealand and South Africa.

Vjosa Isai contributed reporting.