Ann Arbor Air Quality in October
Across 2019–2025, Ann Arbor's October air quality had a median AQI of 36 (Good) over 217 monitored days in the Ann Arbor, MI area. 0.0% of October days (0 of 217) reached Unhealthy for Sensitive Groups or worse, and fine particulate matter (PM2.5) set the daily AQI on 59.0% of days. The cleanest October on record here was 2023 (median AQI 33, 0 days above 100) and the worst was 2022 (median 58, 0 days above 100, peak AQI 98).
- Good: 73.3%
- Moderate: 26.7%
- Unhealthy for Sensitive Groups: 0.0%
- Unhealthy or worse: 0.0%
Improve Indoor Air Quality
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How is the air in Ann Arbor in October?
Good on a typical day: median AQI 36 across 2019–2025, with 0.0% of October days above AQI 100. Fine particulate matter (PM2.5) is the main driver.
- ✓73.3% of October days were Good (AQI 0–50), 26.7% Moderate (51–100).
- ✓0 days of 217 reached AQI 101+; the October peak was 98.
- ✓Best October: 2023; worst October: 2022.
Frequently asked questions
What is the air quality like in Ann Arbor in October?▾
Across 2019–2025, the median daily AQI in Ann Arbor in October was 36 (Good). 73.3% of days were Good, 26.7% Moderate, and 0.0% reached Unhealthy for Sensitive Groups or worse, based on 217 monitored days in EPA's Air Quality System.
Is October a good time for outdoor exercise in Ann Arbor?▾
A typical October day in Ann Arbor sits in the Good range (median AQI 36), so running, cycling and children's outdoor play are fine for everyone on most days; fewer than 1% of October days reached AQI 101+ in 2019–2025.
Which pollutant causes Ann Arbor's October air quality problems?▾
Fine particulate matter (PM2.5) set the daily AQI on 59.0% of October days in Ann Arbor. The highest October AQI recorded in 2019–2025 was 98 (Moderate), in 2022.
Ann Arbor October air quality, year by year
Ann Arbor October air quality by year (Ann Arbor, MI, EPA AQS daily AQI)
| Year | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| 2019 | 31 | 40 | 0 | 71 | PM2.5 |
| 2020 | 31 | 34 | 0 | 59 | PM2.5 |
| 2021 | 31 | 39 | 0 | 59 | PM2.5 |
| 2022worst | 31 | 58 | 0 | 98 | PM2.5 |
| 2023cleanest | 31 | 33 | 0 | 61 | PM2.5 |
| 2024 | 31 | 37 | 0 | 61 | O3 |
| 2025 | 31 | 33 | 0 | 87 | O3 |
What October air means in Ann Arbor
A typical October day in Ann Arbor sits in the Good range (median AQI 36), so running, cycling and children's outdoor play are fine for everyone on most days; fewer than 1% of October days reached AQI 101+ in 2019–2025.
October's median AQI of 36 is below Ann Arbor's whole-year median of 44, making it one of the area's cleaner periods. Nationally, the median October AQI across every EPA metro area (102,872 metro-days, 2019–2025) is 38, so Ann Arbor runs in line with the national October norm; 0.0% of its October days topped AQI 100 versus 1.3% nationally (below average).
October is part of Ann Arbor's fall season (September, October, November); the fall 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.