SmogRank / Countries / United States / Montana

Most polluted cities in Montana, United States

6 measured cities, last 7 days; 0 above the WHO 24-hour guideline. Worst: Great Falls at 9.6 µg/m³, #549 in the world.

5 good  1 moderate

  1. 1Great Falls 9.6
  2. 2Bozeman 6.0
  3. 3Billings 4.9
  4. 4Butte 3.9
  5. 5Helena 3.5
  6. 6Missoula 3.2
Good0–9.0
Moderate9.1–35.4
Sensitive groups35.5–55.4
Unhealthy55.5–125.4
Very unhealthy125.5–225.4
Hazardous225.5+

Estimated: cities without a monitor

Montana cities we can't measure, with model estimates for the last 7 days. Listed by population, not ranked: estimates aren't precise enough to rank. Model estimates from the Copernicus Atmosphere Monitoring Service (CAMS), adjusted to measured cities nearby where there are any. Adjusted, a single day lands within ×1.5 of what a monitor would read about two times in three; unadjusted, it can be off by half or double. Treat them as a guide, not a measurement.

City7-day estimateBand
Kalispell≈ 5 µg/m³Good

Updated 2026-10-01 21:07 UTC. Values are PM2.5 in µg/m³ (fine particles), the median of each city's monitors.