Oakland Best & Worst AQI Days: Air Quality Guide
The worst air quality day on record for Oakland (San Francisco-Oakland-Hayward, CA area) was September 11, 2020, when the daily AQI reached 243 (Very Unhealthy), set by fine particulate matter (PM2.5), in wildfire smoke season. Across 2,287 monitored days in 2019–2025, 10 of the 10 worst days were Unhealthy (AQI 151+) or worse; 9 of the 10 were driven by fine particulate matter (PM2.5) and 1 by ground-level ozone, and 10 of them fell in 2020. The cleanest day was July 24, 2025 at AQI 3 (Good); the 10 best days span 1 different year.
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When were Oakland's worst and best air quality days?
Worst: September 11, 2020, AQI 243 (Very Unhealthy, PM2.5). Best: July 24, 2025, AQI 3 (Good). Based on 2,287 EPA-monitored days in the San Francisco-Oakland-Hayward, CA area, 2019–2025.
- ✓10 of the 10 worst days were Unhealthy (AQI 151+) or worse; the 10th-worst was AQI 160 (Unhealthy).
- ✓Fine particulate matter (PM2.5) drove 9 of the 10 worst days.
- ✓2020 accounts for 10 of the 10 worst days.
Frequently asked questions
What was the worst air quality day in Oakland?▾
September 11, 2020: the San Francisco-Oakland-Hayward, CA area's daily AQI hit 243 (Very Unhealthy), driven by fine particulate matter (PM2.5), in wildfire smoke season. That is the highest of 2,287 monitored days in 2019–2025.
What was the best air quality day in Oakland?▾
July 24, 2025, with a daily AQI of 3 (Good). The daily AQI is the highest reading from any monitor in the area, so even the cleanest day reflects the area's worst monitor.
What was Oakland's worst air quality day in 2025?▾
September 28, 2025, AQI 66 (Moderate), set by fine particulate matter (PM2.5).
Which pollutant causes Oakland's worst air days?▾
Fine particulate matter (PM2.5) set the AQI on 9 of the 10 worst days; ground-level ozone on 1. The tables above list the defining pollutant for every day.
Oakland's 10 worst air quality days, 2019–2025
Highest daily AQI recorded for the San Francisco-Oakland-Hayward, CA area (EPA AQS). The daily AQI is the highest reading from any monitor in the area that day.
| # | Date | AQI | Category | Defining pollutant |
|---|---|---|---|---|
| 1 | (2020 page) | 243 | Very Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
| 2 | (2020 page) | 198 | Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
| 3 | (2020 page) | 198 | Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
| 4 | (2020 page) | 194 | Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
| 5 | (2020 page) | 190 | Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
| 6 | (2020 page) | 185 | Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
| 7 | (2020 page) | 182 | Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
| 8 | (2020 page) | 166 | Unhealthy | O3 — ground-level ozone |
| 9 | (2020 page) | 166 | Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
| 10 | (2020 page) | 160 | Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
Worst day of each year in Oakland
The single highest-AQI day in each year on record. Click a year for its full month-by-month statistics.
| Year | Worst day | AQI | Category | Defining pollutant |
|---|---|---|---|---|
| 2019 | 150 | Unhealthy for Sensitive Groups | O3 — ground-level ozone, in peak ozone season | |
| 2020 | 243 | Very Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season | |
| 2021 | 151 | Unhealthy | O3 — ground-level ozone, in peak ozone season | |
| 2022 | 129 | Unhealthy for Sensitive Groups | O3 — ground-level ozone | |
| 2023 | 130 | Unhealthy for Sensitive Groups | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season | |
| 2024 | 105 | Unhealthy for Sensitive Groups | PM2.5 — fine particulate matter (PM2.5) | |
| 2025 | 66 | Moderate | PM2.5 — fine particulate matter (PM2.5) |
Oakland's 10 best air quality days, 2019–2025
Lowest daily AQI recorded for the San Francisco-Oakland-Hayward, CA area. Ties are listed most recent first.
| # | Date | AQI | Category | Defining pollutant |
|---|---|---|---|---|
| 1 | (2025 page) | 3 | Good | PM2.5 — fine particulate matter (PM2.5) |
| 2 | (2025 page) | 5 | Good | PM2.5 — fine particulate matter (PM2.5) |
| 3 | (2025 page) | 6 | Good | PM2.5 — fine particulate matter (PM2.5) |
| 4 | (2025 page) | 7 | Good | PM2.5 — fine particulate matter (PM2.5) |
| 5 | (2025 page) | 7 | Good | PM2.5 — fine particulate matter (PM2.5) |
| 6 | (2025 page) | 8 | Good | PM2.5 — fine particulate matter (PM2.5) |
| 7 | (2025 page) | 8 | Good | PM2.5 — fine particulate matter (PM2.5) |
| 8 | (2025 page) | 8 | Good | PM2.5 — fine particulate matter (PM2.5) |
| 9 | (2025 page) | 9 | Good | PM2.5 — fine particulate matter (PM2.5) |
| 10 | (2025 page) | 9 | Good | PM2.5 — fine particulate matter (PM2.5) |
Right now in Oakland
The latest EPA AirNow observation puts Oakland's AQI at 37 (PM2.5). The days above are historical records, 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.