Best Cities for Air Quality in Montana
Ranking of cities with the cleanest air in Montana based on AQI data.
Cleanest air in Montana: Billings
Of the 1 Montana metro area EPA published a full year of AQI data for in 2025, Billings recorded the highest share of Good-air days: 315 of 365 monitored days (86.3%) at AQI 50 or below, with a median AQI of 38 and 0 days above AQI 100. Its peak reading that year was AQI 91. The pollutant that set the daily AQI most often was ground-level ozone (220 days).
| # | City (EPA area) | Good days (2025) | Median AQI | Days over 100 | Peak AQI | AQI now |
|---|---|---|---|---|---|---|
| 1 | BillingsBillings, MT | 315 / 365 (86.3%) | 38 | 0 | 91 | 58 |
Figures are EPA's published annual AQI summaries by metropolitan area (Annual AQI by CBSA, 2019–2025), retrieved 2026-09-07. The daily AQI EPA summarises is the highest value any monitor in the area reported that day, so these are metro-area readings, not statewide or rural ones.
Billings's air quality year by year
One clean year can be luck — a mild summer, no wildfire smoke. This is every year EPA has published for the Billings, MT area, so you can see whether Billings's ranking is durable.
| Year | Days measured | Good days | Median AQI | Days over 100 | Days over 150 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|---|---|
| 2019 | 292 | 271 | 31 | 1 | 1 | 159 | fine particulate matter (PM2.5) |
| 2020 | 364 | 304 | 31 | 3 | 1 | 163 | fine particulate matter (PM2.5) |
| 2021 | 340 | 212 | 40 | 10 | 1 | 167 | fine particulate matter (PM2.5) |
| 2022 | 365 | 307 | 32 | 2 | 1 | 155 | fine particulate matter (PM2.5) |
| 2023 | 357 | 306 | 29 | 4 | 1 | 191 | fine particulate matter (PM2.5) |
| 2024 | 357 | 272 | 39 | 1 | 0 | 105 | ground-level ozone |
| 2025 | 365 | 315 | 38 | 0 | 0 | 91 | ground-level ozone |
Across 2020–2025, Billings's air improved: the area's median AQI held near 34 and days above AQI 100 fell from about 5 to 2 per year (comparing the earlier and later halves of the period).
How Montana compares
Ranked by the median of its metro areas' median AQI in 2025, Montana is #5 cleanest of the 51 states EPA publishes metro AQI data for, at a median AQI of 38. The cleanest state on that measure is Alaska; the most polluted is Arizona. See the full state air quality rankings.
| Bordering state | Median metro AQI (2025) | National rank (cleanest first) |
|---|---|---|
| South Dakota | 36 | #3 of 51 |
| North Dakota | 37 | #4 of 51 |
| Wyoming | 45 | #22 of 51 |
| Idaho | 51 | #34 of 51 |
What this ranking does and does not cover
We track 1 Montana city. 1 has a full 2025 EPA record and is ranked above.
EPA's AQI is reported by metropolitan area, and the daily value is the worst reading from any monitor in that area. Rural Montana — and any town without a regulatory monitor — is not represented here. A high Good-day share means the monitored metro air was clean on most days; it is not a statement about a specific street, and it does not capture short pollution spikes between the daily summaries.