A Canadian cold front ushered in a mass of thick Canadian wildfire smoke that badly degraded the air quality across Minnesota on May 18, 2023.
Large wildfires burning in Saskatchewan and Alberta had sent plumes of smoke into parts of Minnesota during the week, but a cold front followed by winds blowing directly from those fires produced an outbreak of ground smoke that dropped visibility to a mile or less across the state. The "smoke front" marched across the state during the day, accompanied by rain in places, and followed by an apparent dimming of the sun, reduced visibility, and at times, a strong campfire aroma. The Minnesota Pollution Control Agency issued Air Quality Alerts for the entire state.
The wildfire smoke contained fine particulates that put the majority of Minnesota in the Red (“Unhealthy”) category in the Air Quality Index. Some of the Pollution Control Agency’s sensors in western Minnesota indicated air quality had degraded into the Purple (“Very Unhealthy”) category at times. The Grand Forks, ND airport reported visibility of a quarter-mile in ground smoke earlier in the day, which is the same visibility threshold used to define heavy snow, dense fog, and blizzard conditions.
Air Quality Advisories begin at when the Air Quality Index (AQI) reaches a value of at least 101, which is the baseline for the Orange or "Unhealthy for Sensitive Groups" category. The Red/Unhealthy category presents risks to the general public and may cause more serious health risks for sensitive groups, and the Purple/Very Unhealthy category increases health risks for everyone.
May 18, 2023