Many fires burning across Canada, forcing evacuations and threatening air quality in the United States, cannot simply be put out, authorities and experts say.

About 17,000 residents of Manitoba in central Canada have been evacuated because of nearly two dozen active wildfires.

As the climate changes, the far north is drying and warming, which means wildfires are getting bigger and more intense. The area burned in Canada is now the second largest on record for this time of year,