Canada’s wildfire smoke has reached Europe, while causing ‘very unhealthy’ conditions in U.S.

Smoke from Canadian wildfires carried another day of poor air quality south of the border to the Midwest, where conditions in parts of Minnesota, Wisconsin and Michigan were rated “very unhealthy” Tuesday.

The fires have forced more than 27,000 Canadians in three provinces to flee their homes, and the smoke has even reached Europe.

The smell of smoke hung over the Minneapolis-St. Paul area on Tuesday morning despite rain that obscured the full measure of the dirty air. The Minnesota...