Smoke from the blazing Minnesota fires in northern Minnesota drifted into Ontario on a recent Wednesday . Environment Canada flagged areas in Ontario among the worst globally for air quality in recent reports . Southern Ontario’s major cities faced urgent warnings about hazardous air from the unrelenting smoke . Dry conditions and strong winds helped wildfires spread at breakneck speed through Minnesota and nearby states. Harmful air drifted north, blanketing Canada in a persistent layer of contaminants.