Health officials from Minnesota to Maine have issued alerts warning of poor air quality from wildfires burning in Canada. People are advised to limit outdoor exposure.

Smoke from Canadian wildfires hovered over several Midwestern states Saturday, bringing warnings of unhealthy air for at least the third day.

Almost 200 wildfires are burning out of control in Canada, including 81 in Saskatchewan, 159 in Manitoba and 61 in Ontario. Figures from the Canadian Interagency Forest Fire Center indicate that more than 16.5 million acres have been scorched so far this year in what will likely be the country’s second-worst wildfire season on record.