Rumbling afternoon thundershowers are breaking over the Southwest, bringing gratitude and sweet relief – not that the region needed much relieving this year. Bouts of cool, wet weather throughout early summer helped stave off the conflagrations predicted to erupt after a dry winter, and by mid-July, most areas had already been deluged by a full month’s worth of rainfall. In other words, summer monsoon season has extinguished any lingering fears that 2014 would be a bad fire year.

“In a word, fire season was underwhelming,” says Chuck Maxwell, meteorologist at the National Interagency Fire Center’s Predictive Services Group. “We had near normal to probably below-normal activity.”

But as the Southwest collectively inhales the smell of rain falling on dry land, parts of the Northwest and Western Canada are bathed in acrid smoke. Nearly a million acres are burning in Washington and Oregon alone – more than what typically burns over the course of a whole year. Some 12,000 firefighters have been deployed since the fires began earlier this month.

Yet though the deadly combination of drought and summer lightning strikes have led to a particularly severe fire season in eastern Washington and Oregon, some of the West’s biggest blazes are in Canada’s Northwest Territories, where the total acreage burned so far this year is six times the 25-year average. In recent years, twice as much Canadian forest has been burning annually as in the 1970s, says University of Alberta wildland fire professor Mike Flannigan, and the northwestern part of the country is experiencing its hottest, driest summer in half a century. “What we are seeing in the Northwest Territories this year is an indicator of what to expect with climate change,” Flannigan says.

While fires in sparsely populated northern Canada have less of an impact on human safety and infrastructure than those in the Pacific Northwest, their effect on the environment may be greater. The ancient, stunted boreal forests that ring the Arctic Circle contain 30 percent of the world’s land-based carbon, and when they burn, that carbon is released into the atmosphere, exacerbating global warming.

But most emissions from boreal fires don’t come from the trees at all – they’re released from the tundra-like peat that makes up the forest floor. The ground literally burns. A study conducted in Indonesia suggests that carbon released from peat fires can equal up to 40 percent of that emitted by global fossil fuels – and making matters worse is that soot from far-northern fires, like those in the Northwest Territories, can darken Arctic ice, making it melt faster.

Wildfire is an integral part of the boreal ecosystem – “the mechanism by which the forest is continually regenerated,” says NASA physicist Forrest Hall. But a 2013 study of charcoal records published in the Proceedings of the National Academy of Science shows that lately, boreal fires have been burning at rates not seen for 10,000 years. Flannigan pins this firmly on climate change, and predicts that increased global warming will spur ever-greater fires in the boreal forests of Alaska, Canada and Russia by the end of the century. That’ll prompt a positive feedback loop in which more boreal fires leads to more global warming, and more global warming leads to more boreal fires.

Yet researchers elsewhere suggest that the deciduous growth that sometimes replaces boreal spruce and fir are less apt to burn than the ecosystem they replace, meaning fires in the taiga may become less severe over time. Either way, as fire sweeps the region, tourists in Yellowknife who’d hoped for a cool northern vacation are instead witnessing something more historic: the ecology of the boreal forest changing before their eyes.