By Erica Dischino, Patrick Wingrove and Amanda Stephenson DULUTH, Minnesota (Reuters) -Smoke from wildfires burning in three Canadian provinces is spreading into the U.S. Upper Midwest, stirring memories of the severe pollution that drifted south from Canada two years ago during that country's worst fire season on record.

Tens of thousands of residents have evacuated across Canada as the wildfire smoke makes its way south to the United States.