SmogRank / World / United States / Montana / March 2023
Most polluted cities in Montana, United States, March 2023
2 cities in Montana, United States ranked by their average PM2.5 over the 31 days. Worst: Butte at 5.9 µg/m³, #698 of 867 cities in the world. Cleanest: Missoula at 3.5. A city needs measurements on 70% of the days to be ranked.
OpenAQ's archive, where our readings come from, has almost none for 20 of these 31 days. Cities in the United States and Europe have them from the EPA's and the European Environment Agency's own records of the same monitors; many cities elsewhere are missing from this board, not clean. Why.
Montana has 10 cities ranked over the last 30 days, but only 2 here: most of its monitors have no readings for March 2023 in OpenAQ's archive, where ours come from, or too few to rank. Cities missing from this board weren't clean, just not measured.
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.
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, March 2023 · All cities in United States, March 2023 · Montana now
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SmogRank, most polluted cities in Montana, United States, PM2.5, March 2023, smogrank.com/us/region/montana/history/2023-03 (accessed 6 Oct 2026).
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.