Unhealthy air has invaded Minnesota, Wisconsin and North Dakota early this week as a new round of wildfire smoke from Canada has wafted into the region, choking out areas as far south as Chicago and Detroit.

BISMARCK, N.D. (AP) — Much of the Upper Midwest on Saturday was dealing with swaths of unhealthy air because of drifting smoke from Canadian wildfires, covering the northern region of the U.S. at a time when people want to be enjoying lakes, trails and the great outdoors.