Ann Arbor Air Quality in May
Across 2019–2025, Ann Arbor's May air quality had a median AQI of 44 (Good) over 217 monitored days in the Ann Arbor, MI area. 0.9% of May days (2 of 217) reached Unhealthy for Sensitive Groups or worse, and ground-level ozone set the daily AQI on 78.3% of days. The cleanest May on record here was 2019 (median AQI 39, 0 days above 100) and the worst was 2023 (median 54, 2 days above 100, peak AQI 129).
- Good: 70.0%
- Moderate: 29.0%
- Unhealthy for Sensitive Groups: 0.9%
- Unhealthy or worse: 0.0%
Improve Indoor Air Quality
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How is the air in Ann Arbor in May?
Good on a typical day: median AQI 44 across 2019–2025, with 0.9% of May days above AQI 100. Ground-level ozone is the main driver.
- ✓70.0% of May days were Good (AQI 0–50), 29.0% Moderate (51–100).
- ✓2 days of 217 reached AQI 101+; the May peak was 129.
- ✓Best May: 2019; worst May: 2023.
Frequently asked questions
What is the air quality like in Ann Arbor in May?▾
Across 2019–2025, the median daily AQI in Ann Arbor in May was 44 (Good). 70.0% of days were Good, 29.0% Moderate, and 0.9% reached Unhealthy for Sensitive Groups or worse, based on 217 monitored days in EPA's Air Quality System.
Is May a good time for outdoor exercise in Ann Arbor?▾
A typical May day in Ann Arbor sits in the Good range (median AQI 44), so running, cycling and children's outdoor play are fine for everyone on most days; fewer than 1% of May days reached AQI 101+ in 2019–2025.
Which pollutant causes Ann Arbor's May air quality problems?▾
Ground-level ozone set the daily AQI on 78.3% of May days in Ann Arbor. The highest May AQI recorded in 2019–2025 was 129 (Unhealthy for Sensitive Groups), in 2023.
Ann Arbor May air quality, year by year
Ann Arbor May air quality by year (Ann Arbor, MI, EPA AQS daily AQI)
| Year | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| 2019cleanest | 31 | 39 | 0 | 58 | O3 |
| 2020 | 31 | 42 | 0 | 56 | O3 |
| 2021 | 31 | 44 | 0 | 93 | O3 |
| 2022 | 31 | 46 | 0 | 97 | O3 |
| 2023worst | 31 | 54 | 2 | 129 | O3 |
| 2024 | 31 | 49 | 0 | 87 | O3 |
| 2025 | 31 | 39 | 0 | 100 | O3 |
What May air means in Ann Arbor
A typical May day in Ann Arbor sits in the Good range (median AQI 44), so running, cycling and children's outdoor play are fine for everyone on most days; fewer than 1% of May days reached AQI 101+ in 2019–2025.
May's median AQI of 44 is in line with Ann Arbor's whole-year median of 44, so this period is neither a clean nor a dirty stretch for the area. Nationally, the median May AQI across every EPA metro area (104,064 metro-days, 2019–2025) is 44, so Ann Arbor runs in line with the national May norm; 0.9% of its May days topped AQI 100 versus 1.3% nationally (about the same).
May is part of Ann Arbor's spring season (March, April, May); the spring page pools all three months.
Activity-specific thresholds: running, cycling, kids' sports.
Right now in Ann Arbor
The latest EPA AirNow observation puts Ann Arbor's AQI at 29 (PM2.5). The figures above are multi-year month 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.