Overview
- State and federal agencies issued air-quality alerts for at least 17 states as smoke from roughly 800–857 Canadian fires plus multiple large northern Minnesota blazes moved over the Midwest and Northeast on Thursday.
- Major population centers reported emergency-grade pollution with Detroit and Minneapolis among the worst globally and cities such as Milwaukee and Chicago recording hazardous to very unhealthy AQI readings.
- Local responses extended from widespread mask distribution and extra cooling centers in New York City to canceled outdoor events and campground evacuations in the Boundary Waters in northern Minnesota.
- Health officials warned that the smoke is rich in fine particulate matter (PM2.5) and gases that penetrate indoors, aggravate asthma and heart disease, and advised staying inside, using filtered air or recirculating A/C, and wearing well-fitting N95/KN95 respirators if outside is unavoidable.
- Forecasters said the worst surface-level smoke should persist through Friday in many areas because of current wind patterns, with an incoming front and rain likely to improve conditions afterward while experts link the unusually large Canadian fire season to hotter, drier conditions that lengthen fire risk.