A rise in zombie fires in Canada is having knock-on effects for the wildfire season. Researchers and fire services are racing to find ways to put out perennial fires. Even at -40C, smoke kept billowing from under the snow. …When the snow melted in early May, these smouldering fires, often called “zombie” fires, came to life again and began to feed on dry trees and brush. The plumes of smoke north of Fort Nelson became a conflagration of 700 sq km. The town is now caught in a horseshoe of fire: to the east, another zombie fire has burned an even larger area, while to the west, a new wildfire has encroached to within 2.5km of the community, damaging properties. … In western Canada, many of these fires went underground and smouldered until this spring, which fire services refer to as “overwintering” or “holdover” fires.