San Francisco Air Quality in August
Across 2019–2025, San Francisco's August air quality had a median AQI of 54 (Moderate) over 195 monitored days in the San Francisco-Oakland-Hayward, CA area. 7.7% of August days (15 of 195) reached Unhealthy for Sensitive Groups or worse, and fine particulate matter (PM2.5) set the daily AQI on 78.5% of days. The cleanest August on record here was 2024 (median AQI 54, 0 days above 100) and the worst was 2020 (median 64, 7 days above 100, peak AQI 182).
- Good: 34.9%
- Moderate: 57.4%
- Unhealthy for Sensitive Groups: 5.1%
- Unhealthy or worse: 2.6%
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How is the air in San Francisco in August?
Moderate on a typical day: median AQI 54 across 2019–2025, with 7.7% of August days above AQI 100. Fine particulate matter (PM2.5) is the main driver.
- ✓34.9% of August days were Good (AQI 0–50), 57.4% Moderate (51–100).
- ✓15 days of 195 reached AQI 101+; the August peak was 182.
- ✓Best August: 2024; worst August: 2020.
Frequently asked questions
What is the air quality like in San Francisco in August?▾
Across 2019–2025, the median daily AQI in San Francisco in August was 54 (Moderate). 34.9% of days were Good, 57.4% Moderate, and 7.7% reached Unhealthy for Sensitive Groups or worse, based on 195 monitored days in EPA's Air Quality System.
Is August a good time for outdoor exercise in San Francisco?▾
A typical August day in San Francisco 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 13 of August days (7.7%) reached AQI 101+ — the level at which EPA advises people with asthma, children and older adults to shorten hard outdoor exertion.
Which pollutant causes San Francisco's August air quality problems?▾
Fine particulate matter (PM2.5) set the daily AQI on 78.5% of August days in San Francisco. The highest August AQI recorded in 2019–2025 was 182 (Unhealthy), in 2020.
San Francisco August air quality, year by year
San Francisco August 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 | 31 | 50 | 3 | 119 | PM2.5 |
| 2020worst | 31 | 64 | 7 | 182 | PM2.5 |
| 2021 | 31 | 60 | 3 | 150 | PM2.5 |
| 2022 | 31 | 50 | 1 | 122 | PM2.5 |
| 2023 | 31 | 57 | 1 | 115 | PM2.5 |
| 2024cleanest | 31 | 54 | 0 | 67 | PM2.5 |
| 2025 | 9 | 19 | 0 | 42 | PM2.5 |
What August air means in San Francisco
A typical August day in San Francisco 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 13 of August days (7.7%) reached AQI 101+ — the level at which EPA advises people with asthma, children and older adults to shorten hard outdoor exertion.
August's median AQI of 54 is in line with San Francisco's whole-year median of 53, so this period is neither a clean nor a dirty stretch for the area. Nationally, the median August AQI across every EPA metro area (104,152 metro-days, 2019–2025) is 45, so San Francisco runs above the national August norm; 7.7% of its August days topped AQI 100 versus 3.5% nationally (above average).
August is part of San Francisco's summer season (June, July, August); the summer page pools all three months.
Activity-specific thresholds: running, cycling, kids' sports.
Right now in San Francisco
The latest EPA AirNow observation puts San Francisco's AQI at 36 (PM2.5). The figures above are multi-year month statistics, not today's reading.
View current San Francisco 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.