Ann Arbor Air Quality in 2021
In 2021, Ann Arbor's air quality (Ann Arbor, MI area) had a median daily AQI of 46 (Good) across 365 monitored days. 0 days (0.0%) reached Unhealthy for Sensitive Groups or worse, 212 were Good, and the year's peak AQI was 100 (Moderate). Fine particulate matter (PM2.5) set the daily AQI on 215 of those days. The cleanest month of 2021 was October (median AQI 39, 0 days above 100) and the worst was July (median 53, 0 days above 100, peak 83).
- Good: 58.1%
- Moderate: 41.9%
- Unhealthy for Sensitive Groups: 0.0%
- Unhealthy or worse: 0.0%
Extra Protection for Ann Arbor Homes
Air quality in Ann Arbor is moderate (AQI 56), with fine particles (PM2.5) the main concern. A True-HEPA purifier gives sensitive groups — kids, seniors and anyone with asthma or allergies — cleaner air indoors on days like today.
Recommended: Coway AP-1512HH Mighty — True HEPA + carbon · CADR ~246 CFM · rooms up to 361 sq ft
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How was Ann Arbor's air quality in 2021?
Good on a typical day: median AQI 46, with 0 days above AQI 100 out of 365 monitored — the 3rd cleanest of 7 years on record for the area.
- ✓Peak AQI in 2021: 100 (Moderate).
- ✓Fine particulate matter (PM2.5) was the main pollutant on 215 days.
- ✓Cleanest month: October; worst: July.
Frequently asked questions
What was the average AQI in Ann Arbor in 2021?▾
EPA's Air Quality System puts Ann Arbor's (Ann Arbor, MI) median daily AQI for 2021 at 46, which is Good. 0 days were Unhealthy for Sensitive Groups or worse and the year's highest AQI was 100.
Which month had the worst air quality in Ann Arbor in 2021?▾
The cleanest month of 2021 was October (median AQI 39, 0 days above 100) and the worst was July (median 53, 0 days above 100, peak 83).
Was 2021 a good or bad year for Ann Arbor's air?▾
Among the 7 years EPA has published for the area (2019–2025), 2021 ranks 3rd cleanest by days above AQI 100. 2021's median of 46 is in line with the area's typical annual median of 44.
Ann Arbor month by month in 2021
Ann Arbor air quality month by month, 2021 (Ann Arbor, MI, EPA AQS daily AQI)
| Month | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| January | 31 | 48 | 0 | 68 | PM2.5 |
| February | 28 | 52 | 0 | 82 | PM2.5 |
| March | 31 | 41 | 0 | 69 | O3 |
| April | 30 | 44 | 0 | 70 | O3 |
| May | 31 | 44 | 0 | 93 | O3 |
| June | 30 | 49 | 0 | 100 | O3 |
| Julyworst | 31 | 53 | 0 | 83 | PM2.5 |
| August | 31 | 52 | 0 | 80 | PM2.5 |
| September | 30 | 42 | 0 | 58 | O3 |
| Octobercleanest | 31 | 39 | 0 | 59 | PM2.5 |
| November | 30 | 43 | 0 | 67 | PM2.5 |
| December | 31 | 42 | 0 | 71 | PM2.5 |
How 2021 compares
Among the 7 years EPA has published for the area (2019–2025), 2021 ranks 3rd cleanest by days above AQI 100.
2021's median of 46 is in line with the area's typical annual median of 44.
Activity-specific thresholds: running, cycling, kids' sports.
Right now in Ann Arbor
The latest EPA AirNow observation puts Ann Arbor's AQI at 56 (PM2.5). The figures above are multi-year annual statistics, not today's reading.
View current Ann Arbor air quality →Source: EPA Air Quality System (AQS) pre-generated Daily AQI by CBSA files — daily AQI by CBSA (Ann Arbor, MI), 2019–2025. Daily AQI per CBSA is the highest AQI reported by any monitor in the area that day; the defining parameter is the pollutant that set it. Month and season statistics pool every such day in the period across all years listed. Retrieved 2026-09-09.