SmogRank / World / United States / Montana / October 2023

Most polluted cities in Montana, United States, October 2023

10 cities in Montana, United States ranked by their average PM2.5 over the 31 days. Worst: Columbia Falls at 8.6 µg/m³, #569 of 1,965 cities in the world. Cleanest: Havre at 3.5. 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 3% 3%0
Every city in Montana, United States ranked for October 2023, 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

All cities in the world, October 2023 · All cities in United States, October 2023 · Montana now

Use this board

SmogRank, most polluted cities in Montana, United States, PM2.5, October 2023, smogrank.com/us/region/montana/history/2023-10 (accessed 6 Oct 2026).

Download top 10 (PNG)

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.