Metro area air quality · 2025
Ann Arbor, MI
Median AQI 41 (Good). 69.3% of monitored days rated Good across this metro's EPA monitoring network.
- 41
- Median AQI
- 69.3%
- Good-air days
- 1
- Unhealthy days
- 43%
- Cleaner than US metros
Ann Arbor, MI posted a 2025 median AQI of 41 (Good) with 69.3% Good days
According to the U.S. EPA Air Quality System, the Ann Arbor, MI CBSA recorded a median AQI of 41 across 365 monitored days in 2025, with 69.3% rated Good and 1 unhealthy or worse. This is an annual metro comparison, not a live advisory.
Data source EPA Air Quality System (AQS)
- Cleaner than US metros
- The Ann Arbor, MI CBSA's 69.3% Good-day share places it cleaner than 43% of US metros in 2025.
- Closest median-AQI peer
- Adrian, MI (69.3% Good, median AQI 41) is the closest nationwide median-AQI peer to Ann Arbor, MI.
- 2020–2025 Good-day shift
- Ann Arbor, MI's Good-day share moved +5.3 points from 2020 to 2025 (median AQI -2).
- Median AQI
- Median AQI: 41
Aggregated from EPA Air Quality System (2025), 365 monitored days. EPA AQS →
The verdict
The Ann Arbor, MI metro runs good on the EPA scale, more polluted than the median US metro, a median AQI of 41 with 69.3% of 365 monitored days in the Good band.
- 41
- median AQI · Good
- 69.3%
- days rated Good
- 43%
- cleaner than US metros
- 152
- worst single reading
1 day reached Unhealthy or worse across the metro's monitors in 2025.
Annual release change
What changed in the 2025 EPA annual release
- Ann Arbor, MI metro's peak single-day AQI rose from 87 to 152 between the 2024 and 2025 EPA annual releases, a change of +65 points.
- Ann Arbor, MI metro's Good-day share rose from 69.1% to 70.7% between the 2024 and 2025 EPA annual releases, a change of +1.5 percentage points.
- Ann Arbor, MI metro's Unhealthy-category days rose from 0 to 1 between the 2024 and 2025 EPA annual releases, a change of +1 days.
Insights: Ann Arbor, MI metro. Aggregated EPA AQS monitors across this Core-Based Statistical Area logged a median Air Quality Index of 41 over 365 measured days in 2025, which corresponds to a Good band and a Moderate metro-wide health grade. The monitored-day split lands at 253 Good days (69%), 104 Moderate (28%), and 7 Unhealthy-for-Sensitive-Groups (2%). The 90th-percentile AQI finished at 68 while the highest single-day reading hit 152 (Unhealthy). Metro residents averaged roughly 20.8 clean-air days per 30-day window across the reporting year.
Across the 2020–2025 trend window, the share of monitored days rated Good shifted by +5.3 points and the median AQI moved -2 points, which classifies the multi-year trajectory as improving. The annual record contains 1 day at Unhealthy or worse. On that day, the EPA recommends that sensitive groups limit prolonged outdoor exertion. Metros with comparable AQI profiles include Adrian, MI (69.3% good, AQI 41); Albany-Schenectady-Troy, NY (67.7% good, AQI 41); Bowling Green, KY (75.6% good, AQI 41).
Air Quality Summary
Median AQI
41
Good
Good Days
69.3%
253 of 365 days
Max AQI
152
Unhealthy
Health Grade
Moderate
90th pct: 68
AQI Day Breakdown (2025)
Distribution of 365 monitored days across EPA AQI categories.
Good
253
69%
Moderate
104
28%
USG
7
2%
Unhealthy
1
0%
Very Unhealthy
0
0%
Hazardous
0
0%
Health Impact Assessment
The Ann Arbor, MI metro area's air quality is rated Moderate based on 69.3% good air days. There were 1 unhealthy days in 2025 when outdoor activity should be limited.
Air quality is acceptable most days, but 7 days reached "Unhealthy for Sensitive Groups" and peak AQI reached 152. Sensitive groups should monitor real-time conditions at AirNow.gov.
How does the Ann Arbor, MI metro compare?
How Ann Arbor, MI compares
5-Year Air Quality Trend
Air quality is improving in the Ann Arbor, MI metro. Best year: 2025 (253 good days).
| Year | Good | Moderate | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|
| 2020 | 236 | 124 | 1 | 43 | 160 |
| 2021 | 212 | 153 | 0 | 46 | 100 |
| 2022 | 222 | 142 | 0 | 46 | 101 |
| 2023 | 168 | 184 | 2 | 52 | 218 |
| 2024 | 253 | 113 | 0 | 43 | 87 |
| 2025 | 253 | 104 | 1 | 41 | 152 |
Metros with a similar median AQI
CBSA peers nationwide whose annual median AQI sits near Ann Arbor, MI (41).
Adrian, MI
Median AQI 41 · 69.3% Good-day share
Albany-Schenectady-Troy, NY
Median AQI 41 · 67.7% Good-day share
Bowling Green, KY
Median AQI 41 · 75.6% Good-day share
Brunswick, GA
Median AQI 41 · 74.3% Good-day share
Decatur, AL
Median AQI 41 · 78.4% Good-day share
Dover, DE
Median AQI 41 · 75.6% Good-day share
Metros with similar unhealthy-day exposure
A second relationship type: metros whose unhealthy-or-worse day count is closest to Ann Arbor, MI's 1 (independent of median AQI).
Bangor, ME
1 unhealthy-or-worse days · median AQI 33
Baraboo, WI
1 unhealthy-or-worse days · median AQI 35
Bartlesville, OK
1 unhealthy-or-worse days · median AQI 44
Beaumont-Port Arthur, TX
1 unhealthy-or-worse days · median AQI 52
Beaver Dam, WI
1 unhealthy-or-worse days · median AQI 40
Bellingham, WA
1 unhealthy-or-worse days · median AQI 31
More Air Quality Data
Explore EPA air quality rankings and guides across U.S. metros and counties.
Cleanest Metro Areas
U.S. metros ranked by their share of Good air-quality days.
Worst Air Quality
Counties and metros with the most unhealthy air days.
All Metro Areas
Annual AQI by CBSA for every monitored U.S. metro area.
Best and Worst City Air
What drives urban air quality and how metro areas compare.
Air Quality Guides
Frequently Asked Questions
What is the air quality in the Ann Arbor, MI metro area? ▼
How many unhealthy air days does Ann Arbor, MI have? ▼
Is air quality in Ann Arbor, MI getting better or worse? ▼
What does AQI 41 mean for health? ▼
What is the 90th percentile AQI for Ann Arbor, MI? ▼
How does Ann Arbor, MI compare to other metro areas? ▼
Data Sources
Primary Source: U.S. Environmental Protection Agency (EPA), Air Quality System (AQS), Annual AQI by CBSA dataset, 2020–2025. See our methodology for how AQI, median, and coverage figures are computed.
Read our methodology , how this data is sourced, computed, and verified.
Source: U.S. EPA Air Quality System (AQS) Annual AQI by CBSA summary files (metro-level) · 2020–2025
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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.