Canada’s emergency preparedness minister is warning that this year’s wildfire season will be worse than the record-breaking season of 2023, when thousands of fires burned tens of millions of acres and set off massive plumes of smoke that enveloped major U.S. cities, including New York and Washington.

This year’s fires could be especially bad in two of the country’s most fire-prone provinces, where nearly 150 of the blazes that started during last year’s season are still burning this winter, under snow-covered ground.

While so-called “zombie fires,” a term recently popularized in the Canadian media, are an annual phenomenon in parts of the country, never have so many fires been reported in a single winter, raising fears that many of them may flare up again above ground.

The “zombie fires” persist during winter because porous peat and moss ground cover in northern areas act as underground fuel for them.

The risk of wildfire in Canada has grown because of climate change, which increases the hot, dry and gusty conditions that have caused drought, according to research published last summer by World Weather Attribution, a group of scientists who model how climate change impacts extreme weather.

Given drought conditions in parts of Western Canada and other extreme weather effects, Harjit Sajjan, Canada’s emergency preparedness minister, said it was not surprising that the wildfire forecast was “alarming.”