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Bemidji, MN Air Quality

EPA monitor data through 2025 · Updated August 13, 2026 · Methods

In 2025, Bemidji, MN recorded 17 days above an Air Quality Index of 100, the level at which EPA begins warning sensitive groups, out of 363 days with monitoring data. Most of those bad days were driven by fine particles. Under the AQI rules that applied before 2013, the same air would have scored 13 days. Since 2015, unhealthy days are 1200% higher on a consistent definition.

Unhealthy days by year, scored two ways

EPA changed what an AQI of 100 means in 2013 and again in 2015, so a count published before those changes is not comparable to one published after. Each panel below applies a single fixed rulebook to every year, so each is internally consistent. Why this matters.

What 2025 looked like

Median AQI 36 · 90th-percentile AQI 69 · worst day 191. Scored under current rules.

What drove the unhealthy days

Of the 17 days above 100 in 2025, 4 were driven by ozone and 13 by fine particles. The two behave differently. Ozone peaks on hot sunny afternoons; fine particles now spike mainly with wildfire smoke. In the eastern United States, ozone has stopped responding to emission cuts: nitrogen oxide emissions kept falling after 2014 and ambient ozone barely moved.

The unhealthy days in 2025

Every day the index passed 100, what it reached, and which pollutant drove it. 4 of these 17 would not have counted as unhealthy under the pre-2013 rules.

Statewide context

Bemidji, MN sits in Minnesota.

The full series

Sources

• EPA AirData daily monitor files, recomputed under both breakpoint tables. Methods and validation.
• Download the full dataset for every state and metro.