State air quality · 2025
Michigan Air Quality Ranking
Across 27 monitored counties, the typical county in Michigan posts a median AQI of 38 (Good) and 74.7% of monitored days were rated Good, from EPA AQS.
- 38
- Avg median AQI
- 74.7%
- Good-air days
- 27
- Counties monitored
- 40%
- Cleaner than US states
Michigan's typical county median AQI is 38 (Good) across 27 monitored counties
According to the U.S. EPA Air Quality System, Michigan monitors 27 counties with a day-weighted Good-day share of 74.7%. Cleanest: Wexford County (94.2% Good). Most polluted: Wayne County (36.2%). These are annual summaries, not live AirNow readings.
Data source EPA Air Quality System (AQS)
- Cleaner than US states
- Michigan's day-weighted Good-day share of 74.7% places it cleaner than 40% of US states.
- In-state spread
- Within Michigan, Keweenaw County leads at 100.0% Good days while Wayne County sits at 36.2% across 27 monitored counties.
- 2024→2025 release
- Michigan's Good-day share moved -1.1 points vs the 2024 EPA annual release.
- Typical median AQI
- Typical median AQI: 38
Verify with AirNow → · EPA AQS →
EPA state monitoring brief
AQS state key MICHIGAN
Michigan · 2025 EPA AQS · 27 counties · med AQI 38 · 74.7% Good · Wexford→Wayne spread
- GOOD 38 Median AQI · Good
- SHARE 74.7% Good-day share
- COUNT 27 Counties monitored
- UNH 27 Unhealthy+ days
- RANK 40% Cleaner than states
- O3 55.7% Main pollutant share
Michigan's 74.7% Good-day share is cleaner than 40% of monitored US states; Wexford and Wayne County bracket the in-state range. Open Keweenaw County →
According to EPA AQS annual summaries on PlainAirData, Michigan ranks #32 of 52 by day-weighted good-day share (74.7%) and #18 by mean county median AQI (37.7). 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
74.7%
Good-day share in 2025, down 1.1 percentage points vs 2024. County-mean median AQI 38, within half a point of the 2024 county-mean median.
Pollutant mix
Ozone
Main driver on 55.7% of pollutant-assigned days.
- Ozone 55.7%
- PM2.5 43.4%
- PM10 0.8%
- NO2 0.1%
Monitoring coverage
301
Average monitored days per county in the latest release. 2 of 27 counties sit below the 100-day floor used for cleanest/most-polluted claims.
Counties Monitored
27
Good Days %
74.7%
Avg Median AQI
38
Total Unhealthy Days
27
Best Air Quality
Wexford County
Worst Air Quality
Wayne County
Where Michigan sits nationally
COUNT-derived placement among 52 US states with at least 365 monitored days in the latest county release. Michigan's day-weighted Good-day share is 74.7% - cleaner than 40% of that comparison set.
Michigan Good-day share vs. every US state
Day-weighted share of monitored days in the Good band (AQI 0–50) - EPA AQS annual release
74.7% 40th percentile higher than 40% 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 Michigan have the cleanest and most polluted air?
Cleanest counties in Michigan
| County | Good % | Median AQI | Max AQI | Unhealthy Days |
|---|---|---|---|---|
| Keweenaw | 100.0% | 8 | 31 | 0 |
| Monroe | 94.9% | 18 | 77 | 0 |
| Wexford | 94.2% | 36 | 93 | 0 |
| Tuscola | 91.9% | 35 | 112 | 0 |
| Benzie | 91.1% | 35 | 80 | 0 |
| Clinton | 90.2% | 39 | 119 | 0 |
| Huron | 89.6% | 38 | 108 | 0 |
| Mason | 89.2% | 36 | 87 | 0 |
| Missaukee | 86.9% | 35 | 133 | 0 |
| Cass | 85.3% | 40 | 115 | 0 |
| Muskegon | 83.5% | 39 | 140 | 0 |
| Schoolcraft | 83.4% | 33 | 167 | 2 |
| Genesee | 83.2% | 38 | 126 | 0 |
| Marquette | 82.4% | 19 | 193 | 6 |
| Berrien | 80.9% | 41 | 147 | 0 |
| Manistee | 79.5% | 33 | 167 | 3 |
| Ingham | 72.6% | 38 | 153 | 1 |
| Ottawa | 71.2% | 40 | 159 | 1 |
| Bay | 70.4% | 39 | 139 | 0 |
| Macomb | 70.1% | 40 | 166 | 2 |
| St. Clair | 69.6% | 39 | 152 | 1 |
| Lenawee | 69.3% | 41 | 147 | 0 |
| Washtenaw | 69.3% | 41 | 152 | 1 |
| Oakland | 69.1% | 41 | 166 | 2 |
| Allegan | 63.9% | 44 | 151 | 2 |
| Kalamazoo | 61.4% | 43 | 156 | 1 |
| Kent | 41.9% | 52 | 163 | 2 |
| Wayne | 36.2% | 54 | 156 | 3 |
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: 27 counties in Michigan 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.