Canada's worst-ever wildfire season has choked much of North America with dangerous smoke for months, coupling with deadly heat around the globe in a summer that's focusing the world's attention on the perils of climate change.
By this week, some 42,000 square miles (109,000 square kilometers) had burned — an area roughly equivalent to the U.S. state of Virginia. About 900 fires were actively burning, with only about one-fifth considered under control.
