San Francisco Air Quality in Summer
Across 2019–2025, San Francisco's summer (June–August) air quality had a median AQI of 53 (Moderate) over 579 monitored days in the San Francisco-Oakland-Hayward, CA area. 5.3% of summer days (31 of 579) reached Unhealthy for Sensitive Groups or worse, and fine particulate matter (PM2.5) set the daily AQI on 76.5% of days. The cleanest summer on record here was 2025 (median AQI 19, 0 days above 100) and the worst was 2023 (median 58, 9 days above 100, peak AQI 115).
- Good: 39.7%
- Moderate: 54.9%
- Unhealthy for Sensitive Groups: 4.3%
- Unhealthy or worse: 1.0%
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How is the air in San Francisco in summer?
Moderate on a typical day: median AQI 53 across 2019–2025, with 5.3% of summer days above AQI 100. Fine particulate matter (PM2.5) is the main driver.
- ✓39.7% of summer days were Good (AQI 0–50), 54.9% Moderate (51–100).
- ✓31 days of 579 reached AQI 101+; the summer peak was 182.
- ✓Cleanest month: July; worst month: August.
Frequently asked questions
What is the air quality like in San Francisco in summer?▾
Across 2019–2025, the median daily AQI in San Francisco in summer was 53 (Moderate). 39.7% of days were Good, 54.9% Moderate, and 5.3% reached Unhealthy for Sensitive Groups or worse, based on 579 monitored days in EPA's Air Quality System.
Is summer a good time for outdoor exercise in San Francisco?▾
A typical summer day in San Francisco is Moderate (median AQI 53): outdoor exercise is acceptable for most people, but unusually sensitive individuals should watch for symptoms, and about 1 day in 19 of summer days (5.3%) 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 summer air quality problems?▾
Fine particulate matter (PM2.5) set the daily AQI on 76.5% of summer days in San Francisco. The highest summer AQI recorded in 2019–2025 was 182 (Unhealthy), in 2023.
San Francisco summer air quality, year by year
San Francisco summer 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 | 92 | 53 | 8 | 150 | PM2.5 |
| 2020 | 92 | 53 | 8 | 182 | PM2.5 |
| 2021 | 92 | 54 | 5 | 151 | PM2.5 |
| 2022 | 92 | 50 | 1 | 122 | PM2.5 |
| 2023worst | 92 | 58 | 9 | 115 | PM2.5 |
| 2024 | 92 | 56 | 0 | 98 | PM2.5 |
| 2025cleanest | 27 | 19 | 0 | 56 | PM2.5 |
What summer air means in San Francisco
A typical summer day in San Francisco is Moderate (median AQI 53): outdoor exercise is acceptable for most people, but unusually sensitive individuals should watch for symptoms, and about 1 day in 19 of summer days (5.3%) reached AQI 101+ — the level at which EPA advises people with asthma, children and older adults to shorten hard outdoor exertion.
Summer's median AQI of 53 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 Summer AQI across every EPA metro area (308,645 metro-days, 2019–2025) is 46, so San Francisco runs above the national Summer norm; 5.3% of its Summer days topped AQI 100 versus 3.6% nationally (above average).
Within the season, July is the cleanest month (median AQI 53, 4.1% of days above 100) and August the worst (median 54, 7.7% above 100).
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 season 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.