SmogRank / World / United States / Montana / August 2026

Most polluted cities in Montana, United States, August 2026

10 cities in Montana, United States ranked by their average PM2.5 over the 31 days. Worst: Columbia Falls at 29.8 µg/m³, #113 of 2,866 cities in the world. Cleanest: Havre at 10.2. A city needs measurements on 70% of the days to be ranked.

Ranked by unhealthy days: the share of each city's measured days with a daily mean over 35.4 µg/m³ (US AQI 101+), Unhealthy for Sensitive Groups or worse on the US EPA's scale. Ties go to the higher average.

← Columbia Falls 26% 20%0

Every city in Montana, United States ranked for August 2026, one column each, ranked by unhealthy days: height is the share of its measured days that were unhealthy, colour its average. Point at it to read a city; tap to open it.

Good0–50

Moderate51–100

Sensitive groups101–150

Unhealthy151–200

Very unhealthy201–300

Hazardous301+

The US EPA's Air Quality Index for PM2.5 (2024 breakpoints). Show values as: µg/m³ · US AQI · India AQI · China AQI · European AQI · UK DAQI · Canada AQHI+. About the scales

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SmogRank, most polluted cities in Montana, United States, PM2.5, August 2026, smogrank.com/us/region/montana/history/2026-08 (accessed 6 Oct 2026).

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You're welcome to reuse a single chart, image or figure with this citation and a link. Terms. Raw monitor readings in bulk are published by OpenAQ, under each provider's licence.