All of south-central Pennsylvania remained under a Code Purple air quality alert Friday, with purple-to-maroon readings showing very unhealthy to hazardous smoke conditions across the Susquehanna Valley.
Smoke from wildfires in southern Ontario and northern Minnesota spread across the Great Lakes and Northeast, driving the Air Quality Index above 200 — an extremely rare level for the region.
Residents were urged to keep windows closed, run HVAC on recirculate, limit outdoor time and watch for coughing or shortness of breath as temperatures neared 90 degrees under a hazy sky.
Conditions are expected to stay harmful through Friday night, then improve Saturday as winds shift and a warm front helps lift the smoke; forecasts show poor air Saturday and moderate air by Sunday and Monday.