| # | County | Median AQI |
|---|---|---|
| 1 | Lincoln County | 49 |
| 2 | Cascade County | 46 |
| 3 | Lewis and Clark County | 46 |
| 4 | Missoula County | 43 |
| 5 | Flathead County | 42 |
| 6 | Fergus County | 40 |
| 7 | Yellowstone County | 39 |
| 8 | Custer County | 36 |
| 9 | Richland County | 36 |
| 10 | Silver Bow County | 31 |
| 11 | Ravalli County | 24 |
| 12 | Glacier County | 23 |
| 13 | Phillips County | 21 |
| 14 | Sanders County | 21 |
| 15 | Gallatin County | 18 |
| 16 | Sheridan County | 17 |
| 17 | Hill County | 15 |
| 18 | Dawson County | 14 |
| 19 | Roosevelt County | 13 |
| 20 | Teton County | 13 |
| 21 | Beaverhead County | 12 |
| 22 | Powell County | 12 |
| 23 | Lake County | 9 |
| 24 | Rosebud County | 4 |
Source: EPA Air Quality Index annual summary (2024). All counties with data are ranked. Estimates carry margins of error.
Citing this page: GIS Map, “Counties with the Worst Air Quality in Montana”, https://gismap.land/rankings/montana/worst-air-quality-counties. Figures from EPA Air Quality Index annual summary (2024).
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