Smoke from the explosive forest fires in Minnesota drifted into southern Ontario on a recent Wednesday . Environment Canada reported areas in Ontario among the worst globally for air quality during this stretch. Southern Ontario’s major cities faced urgent warnings about hazardous air from the unrelenting smoke . Extreme drought and strong winds helped fires spread at breakneck speed through Minnesota and nearby states. Polluted haze drifted north, blanketing Canada in a heavy curtain of contaminants.