Detroit Air Quality in September
Across 2019–2025, Detroit's September air quality had a median AQI of 55 (Moderate) over 210 monitored days in the Detroit-Warren-Dearborn, MI area. 0.5% of September days (1 of 210) reached Unhealthy for Sensitive Groups or worse, and fine particulate matter (PM2.5) set the daily AQI on 83.3% of days. The cleanest September on record here was 2021 (median AQI 49, 0 days above 100) and the worst was 2025 (median 54, 1 day above 100, peak AQI 108).
- Good: 33.3%
- Moderate: 66.2%
- Unhealthy for Sensitive Groups: 0.5%
- Unhealthy or worse: 0.0%
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How is the air in Detroit in September?
Moderate on a typical day: median AQI 55 across 2019–2025, with 0.5% of September days above AQI 100. Fine particulate matter (PM2.5) is the main driver.
- ✓33.3% of September days were Good (AQI 0–50), 66.2% Moderate (51–100).
- ✓1 day of 210 reached AQI 101+; the September peak was 108.
- ✓Best September: 2021; worst September: 2025.
Frequently asked questions
What is the air quality like in Detroit in September?▾
Across 2019–2025, the median daily AQI in Detroit in September was 55 (Moderate). 33.3% of days were Good, 66.2% Moderate, and 0.5% reached Unhealthy for Sensitive Groups or worse, based on 210 monitored days in EPA's Air Quality System.
Is September a good time for outdoor exercise in Detroit?▾
A typical September day in Detroit is Moderate (median AQI 55): outdoor exercise is acceptable for most people, but unusually sensitive individuals should watch for symptoms, and fewer than 1% of September days reached AQI 101+ — the level at which EPA advises people with asthma, children and older adults to shorten hard outdoor exertion.
Which pollutant causes Detroit's September air quality problems?▾
Fine particulate matter (PM2.5) set the daily AQI on 83.3% of September days in Detroit. The highest September AQI recorded in 2019–2025 was 108 (Unhealthy for Sensitive Groups), in 2025.
Detroit September air quality, year by year
Detroit September air quality by year (Detroit-Warren-Dearborn, MI, EPA AQS daily AQI)
| Year | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| 2019 | 30 | 56 | 0 | 87 | PM2.5 |
| 2020 | 30 | 54 | 0 | 82 | PM2.5 |
| 2021cleanest | 30 | 49 | 0 | 95 | PM2.5 |
| 2022 | 30 | 53 | 0 | 84 | PM2.5 |
| 2023 | 30 | 60 | 0 | 82 | PM2.5 |
| 2024 | 30 | 55 | 0 | 84 | PM2.5 |
| 2025worst | 30 | 54 | 1 | 108 | PM2.5 |
What September air means in Detroit
A typical September day in Detroit is Moderate (median AQI 55): outdoor exercise is acceptable for most people, but unusually sensitive individuals should watch for symptoms, and fewer than 1% of September days reached AQI 101+ — the level at which EPA advises people with asthma, children and older adults to shorten hard outdoor exertion.
September's median AQI of 55 is in line with Detroit's whole-year median of 58, so this period is neither a clean nor a dirty stretch for the area. Nationally, the median September AQI across every EPA metro area (100,699 metro-days, 2019–2025) is 43, so Detroit runs above the national September norm; 0.5% of its September days topped AQI 100 versus 2.7% nationally (below average).
September is part of Detroit's fall season (September, October, November); the fall page pools all three months.
Activity-specific thresholds: running, cycling, kids' sports.
Right now in Detroit
The latest EPA AirNow observation puts Detroit's AQI at 29 (PM2.5). The figures above are multi-year month statistics, not today's reading.
View current Detroit air quality →Source: EPA Air Quality System (AQS) pre-generated Daily AQI by CBSA files — daily AQI by CBSA (Detroit-Warren-Dearborn, 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.