State air quality · 2025
Wyoming Air Quality Ranking
Across 17 monitored counties, the typical county in Wyoming posts a median AQI of 31 (Good) and 85.1% of monitored days were rated Good, from EPA AQS.
- 31
- Avg median AQI
- 85.1%
- Good-air days
- 17
- Counties monitored
- 90%
- Cleaner than US states
Wyoming's typical county median AQI is 31 (Good) across 17 monitored counties
According to the U.S. EPA Air Quality System, Wyoming monitors 17 counties with a day-weighted Good-day share of 85.1%. Cleanest: Carbon County (100.0% Good). Most polluted: Albany County (55.6%). These are annual summaries, not live AirNow readings.
Data source EPA Air Quality System (AQS)
- Cleaner than US states
- Wyoming's day-weighted Good-day share of 85.1% places it cleaner than 90% of US states.
- In-state spread
- Within Wyoming, Carbon County leads at 100.0% Good days while Albany County sits at 55.6% across 17 monitored counties.
- 2024→2025 release
- Wyoming's Good-day share moved +5.1 points vs the 2024 EPA annual release.
- Typical median AQI
- Typical median AQI: 31
Verify with AirNow → · EPA AQS →
EPA state monitoring brief
AQS state key WYOMING
Wyoming · 2025 EPA AQS · 17 counties · med AQI 31 · 85.1% Good · Carbon→Albany spread
- GOOD 31 Median AQI · Good
- SHARE 85.1% Good-day share
- COUNT 17 Counties monitored
- UNH 15 Unhealthy+ days
- RANK 90% Cleaner than states
- O3 58.9% Main pollutant share
Good-day share peers
Wyoming's 85.1% Good-day share is cleaner than 90% of monitored US states; Carbon and Albany County bracket the in-state range. Open Carbon County →
According to EPA AQS annual summaries on PlainAirData, Wyoming ranks #5 of 52 by day-weighted good-day share (85.1%) and #6 by mean county median AQI (31.4). Hawaii is #1 of 52 by day-weighted good-day share (93.8% of monitored days) at mean county median-AQI #4 (27.3) ≠ Alaska #1 lowest mean county median AQI (20.3) at good-day share #8 (84.4%).
Data updated August 2026
What changed, what drives it, and how thick is the sample
Three derived views WPR-style word count does not substitute for: release-over-release movement from county annual rows, the EPA main-pollutant day mix, and how many counties sit below the 100-day ranking floor.
Release change
85.1%
Good-day share in 2025, up 5.1 percentage points vs 2024. County-mean median AQI 31, 3.1 points lower (cleaner) than 2024.
Pollutant mix
Ozone
Main driver on 58.9% of pollutant-assigned days.
- Ozone 58.9%
- PM10 19.4%
- PM2.5 16.9%
- NO2 4.8%
Monitoring coverage
357
Average monitored days per county in the latest release. Every monitored county clears the 100-day ranking floor.
Counties Monitored
17
Good Days %
85.1%
Avg Median AQI
31
Total Unhealthy Days
15
Best Air Quality
Carbon County
Worst Air Quality
Albany County
Where Wyoming sits nationally
COUNT-derived placement among 52 US states with at least 365 monitored days in the latest county release. Wyoming's day-weighted Good-day share is 85.1% - cleaner than 90% of that comparison set.
Wyoming Good-day share vs. every US state
Day-weighted share of monitored days in the Good band (AQI 0–50) - EPA AQS annual release
85.1% Cleaner than 90% higher than 90% of 52 US states
Each bar is a band; taller bars hold more US states. The dashed line + filled bar mark this entry. Hover or tap any bar for its full count, share, and where it sits relative to this entry.
Source U.S. Environmental Protection Agency, Air Quality System (AQS) · 2025
Which counties in Wyoming have the cleanest and most polluted air?
Cleanest counties in Wyoming
| County | Good % | Median AQI | Max AQI | Unhealthy Days |
|---|---|---|---|---|
| Carbon | 100.0% | 8 | 43 | 0 |
| Uinta | 100.0% | 9 | 50 | 0 |
| Lincoln | 98.9% | 10 | 77 | 0 |
| Park | 98.0% | 13 | 73 | 0 |
| Washakie | 96.3% | 8 | 68 | 0 |
| Converse | 96.2% | 40 | 63 | 0 |
| Johnson | 92.8% | 41 | 84 | 0 |
| Platte | 90.6% | 15 | 723 | 9 |
| Big Horn | 89.2% | 39 | 119 | 0 |
| Sheridan | 89.1% | 27 | 75 | 0 |
| Weston | 87.7% | 39 | 136 | 0 |
| Natrona | 86.3% | 42 | 76 | 0 |
| Teton | 84.9% | 44 | 90 | 0 |
| Laramie | 75.1% | 45 | 108 | 0 |
| Campbell | 74.3% | 44 | 156 | 1 |
| Sweetwater | 72.9% | 44 | 118 | 0 |
| Sublette | 70.1% | 47 | 164 | 3 |
| Fremont | 69.6% | 47 | 100 | 0 |
| Albany | 55.6% | 49 | 172 | 2 |
Data Sources
Primary Source: U.S. Environmental Protection Agency (EPA), Air Quality System (AQS), Annual AQI by County dataset, 2020–2025. See our methodology for how AQI and median figures are computed.
Coverage: 17 counties in Wyoming with active monitoring stations. Unmonitored counties are not represented.
Source: U.S. EPA Air Quality System (AQS) Annual AQI by county summary files, aggregated to the state level · 2020–2025
Every figure on PlainAirData is rendered directly from EPA AQS air-quality monitoring data, no number is typed in by an editor. This page draws directly on EPA AQS air-quality monitoring data, no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error.
Informational only, not professional advice. Data from EPA AQS. See our disclaimer.