Best Cities for Air Quality in Wyoming
Ranking of cities with the cleanest air in Wyoming based on AQI data.
Cleanest air in Wyoming: Cheyenne
Of the 1 Wyoming metro area EPA published a full year of AQI data for in 2025, Cheyenne recorded the highest share of Good-air days: 274 of 365 monitored days (75.1%) at AQI 50 or below, with a median AQI of 45 and 1 day above AQI 100. Its peak reading that year was AQI 108. The pollutant that set the daily AQI most often was ground-level ozone (345 days).
| # | City (EPA area) | Good days (2025) | Median AQI | Days over 100 | Peak AQI | AQI now |
|---|---|---|---|---|---|---|
| 1 | CheyenneCheyenne, WY | 274 / 365 (75.1%) | 45 | 1 | 108 | 27 |
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.
Cheyenne'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 Cheyenne, WY area, so you can see whether Cheyenne's ranking is durable.
| Year | Days measured | Good days | Median AQI | Days over 100 | Days over 150 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|---|---|
| 2019 | 365 | 296 | 43 | 0 | 0 | 74 | ground-level ozone |
| 2020 | 366 | 313 | 39 | 5 | 2 | 159 | ground-level ozone |
| 2021 | 364 | 261 | 44 | 11 | 0 | 126 | ground-level ozone |
| 2022 | 363 | 297 | 42 | 0 | 0 | 90 | ground-level ozone |
| 2023 | 365 | 275 | 45 | 5 | 1 | 156 | ground-level ozone |
| 2024 | 366 | 271 | 45 | 4 | 1 | 151 | ground-level ozone |
| 2025 | 365 | 274 | 45 | 1 | 0 | 108 | ground-level ozone |
Across 2019–2025, Cheyenne's air quality shows no clear trend: the area's median AQI held near 42 and days above AQI 100 fell from about 5 to 3 per year (comparing the earlier and later halves of the period).
How Wyoming compares
Ranked by the median of its metro areas' median AQI in 2025, Wyoming is #22 cleanest of the 51 states EPA publishes metro AQI data for, at a median AQI of 45. The cleanest state on that measure is Alaska; the most polluted is Arizona. See the full state air quality rankings.
What this ranking does and does not cover
We track 1 Wyoming 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 Wyoming — 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.