Oakland Air Quality in September
Across 2019–2025, Oakland's September air quality had a median AQI of 54 (Moderate) over 190 monitored days in the San Francisco-Oakland-Hayward, CA area. 10.0% of September days (19 of 190) reached Unhealthy for Sensitive Groups or worse, and fine particulate matter (PM2.5) set the daily AQI on 83.7% of days. The cleanest September on record here was 2025 (median AQI 21, 0 days above 100) and the worst was 2020 (median 88, 11 days above 100, peak AQI 243).
- Good: 32.6%
- Moderate: 57.4%
- Unhealthy for Sensitive Groups: 6.8%
- Unhealthy or worse: 3.2%
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How is the air in Oakland in September?
Moderate on a typical day: median AQI 54 across 2019–2025, with 10.0% of September days above AQI 100. Fine particulate matter (PM2.5) is the main driver.
- ✓32.6% of September days were Good (AQI 0–50), 57.4% Moderate (51–100).
- ✓19 days of 190 reached AQI 101+; the September peak was 243.
- ✓Best September: 2025; worst September: 2020.
Frequently asked questions
What is the air quality like in Oakland in September?▾
Across 2019–2025, the median daily AQI in Oakland in September was 54 (Moderate). 32.6% of days were Good, 57.4% Moderate, and 10.0% reached Unhealthy for Sensitive Groups or worse, based on 190 monitored days in EPA's Air Quality System.
Is September a good time for outdoor exercise in Oakland?▾
A typical September day in Oakland is Moderate (median AQI 54): outdoor exercise is acceptable for most people, but unusually sensitive individuals should watch for symptoms, and about 1 day in 10 of September days (10.0%) reached AQI 101+ — the level at which EPA advises people with asthma, children and older adults to shorten hard outdoor exertion.
Which pollutant causes Oakland's September air quality problems?▾
Fine particulate matter (PM2.5) set the daily AQI on 83.7% of September days in Oakland. The highest September AQI recorded in 2019–2025 was 243 (Very Unhealthy), in 2020.
Oakland September air quality, year by year
Oakland September air quality by year (San Francisco-Oakland-Hayward, CA, EPA AQS daily AQI)
| Year | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| 2019 | 30 | 48 | 0 | 97 | PM2.5 |
| 2020worst | 30 | 88 | 11 | 243 | PM2.5 |
| 2021 | 30 | 59 | 3 | 129 | PM2.5 |
| 2022 | 30 | 57 | 2 | 129 | PM2.5 |
| 2023 | 30 | 54 | 3 | 130 | PM2.5 |
| 2024 | 30 | 53 | 0 | 67 | PM2.5 |
| 2025cleanest | 10 | 21 | 0 | 66 | PM2.5 |
What September air means in Oakland
A typical September day in Oakland is Moderate (median AQI 54): outdoor exercise is acceptable for most people, but unusually sensitive individuals should watch for symptoms, and about 1 day in 10 of September days (10.0%) 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 54 is in line with Oakland's whole-year median of 53, 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 Oakland runs above the national September norm; 10.0% of its September days topped AQI 100 versus 2.7% nationally (above average).
September is part of Oakland's fall season (September, October, November); the fall page pools all three months.
Activity-specific thresholds: running, cycling, kids' sports.
Right now in Oakland
The latest EPA AirNow observation puts Oakland's AQI at 37 (PM2.5). The figures above are multi-year month statistics, not today's reading.
View current Oakland air quality →Source: EPA Air Quality System (AQS) pre-generated Daily AQI by CBSA files — daily AQI by CBSA (San Francisco-Oakland-Hayward, CA), 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.