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.

Air quality in some parts of the United States is being compromised as smoke from dozens of wildfires in Canada travels south, pushed by winds high in the atmosphere.

National Weather Service officials are expecting patchy smoke from Canadian wildfires to move into the Chicago area Friday along with a 30% chance of showers and thunderstorms.