Graph of maximum daily Air Quality Index (AQI) values in Minnesota from late July showing 9-day, run from July 29 through August 6 with Orange or worse values somewhere in the state. Image produced by Minnesota State Climatology Office with data from Minnesota Pollution Control Agency.
Following bouts of heat, humidity, and storms July 27th to early the 29th, Minnesotans expecting a a refreshing northerly breeze instead got mouthfuls of thick Canadian smoke, this time lasting over a week in some places.
By the afternoon of Tuesday July 29th, heavy smoke had settled into northern Minnesota. It spread across most of the rest of the state on Wednesday, lasting into the weekend statewide, and lingering in northern and northeastern Minnesota until Wednesday August 6th.
This was not the first, nor the most severe smoke outbreak of summer, but it was by far the longest. During each of the nine days, from July 29th through August 6th, some part of Minnesota recorded a daily Air Quality Index (AQI) value of over 100 (the "orange" category, considered unhealthy for sensitive groups), with values exceeding 150 ("red," unhealthy for everyone) on five of those days and 200 ("purple," or very unhealthy) on one day, July 30th. By comparison, the significant smoke outbreaks of early June and mid-July had 3 or 4 days each with orange or higher daily AQI levels. The only other comparably-long stretch during since records began about a decade ago, covered the exact same dates, July 29th to August 6th, in 2021.
August 11, 2025
KAB