Smoke from wildfires in Canada has begun drifting across the border into the United States, raising concerns on Friday about possible health hazards in the Upper Midwest, the authorities said.

All of Minnesota will experience poor air quality this weekend as smoke — both near the surface and at higher altitudes — invades from wildfires that are burning out of control in Canada.

Both Saskatchewan and Manitoba have declared states of emergency for the next month and asked for international help in fighting the fires.