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 in recent reports . Toronto faced urgent warnings about hazardous air from the unrelenting smoke . Prolonged dryness and howling winds helped blazes spread at breakneck speed through Minnesota and nearby states. Harmful air drifted north, blanketing Canada in a persistent layer of contaminants.