The air in the Upper Midwest is so thick, ‘if you have a nice pork loin you can hang from a tree, it’ll turn into ham’

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.

Most of Minnesota and parts of Montana, North Dakota and Wisconsin were ranked “unhealthy” for air quality on a U.S. Environmental Protection Agency map. Part of North Dakota that is home to Theodore Roosevelt National Park and other tourist...