San Francisco air quality
California, United States · Live AQI and hourly forecast for the next 5 days · updated Sat 5:00 PM local time
Good
Great air. A perfect time to be outside.
- Next 24 hours
- 44–53US AQI, highest around Sun 4:00 PM
- Best time outside
- Sat 5:00 PM–8:00 PMUS AQI about 45
- PM2.5 vs WHO guideline
- 0.7×10 µg/m³ over 24 h, guideline 15
- Cigarette equivalent
- ≈ 0.5 a dayBerkeley Earth rule of thumb
- European AQI
- Fairlevel 2 of 6
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Pollutants in San Francisco right now
| Pollutant | Now | Next 24 h vs WHO | US AQI band |
|---|---|---|---|
| Fine particles (PM2.5) | 9.9 µg/m³ | 0.7× | Moderate |
| Coarse particles (PM10) | 15 µg/m³ | 0.4× | Good |
| Nitrogen dioxide (NO2) | 4.0 µg/m³ | 0.3× | Good |
| Ozone (O3) | 71 µg/m³ | 0.7× | Good |
| Sulphur dioxide (SO2) | 0.8 µg/m³ | 0.0× | Good |
| Carbon monoxide (CO) | 118 µg/m³ | 0.0× | Good |
| Desert dust | 0 µg/m³ | ||
| Smoke and haze (aerosol optical depth) | 0.07 | ||
| UV index | 1.0 |
“Next 24 h vs WHO” compares the forecast with the World Health Organization’s 2021 guideline levels: 24-hour means of 15 µg/m³ for PM2.5, 45 for PM10, 25 for NO2, 40 for SO2 and 4 mg/m³ for CO, and 100 µg/m³ over 8 hours for ozone. Above 1× is above the guideline.
Next 48 hours
Hourly US AQI. Highest 55 around Mon 12:00 PM, lowest 44 around Sat 5:00 PM.
5-day air quality forecast for San Francisco
Daily range of the hourly US AQI, from lowest to highest, on a scale of 0 to 150.
| Day | US AQI | At worst | PM2.5 avg | |
|---|---|---|---|---|
| Sat, Sep 26 | 37–50 | 9.1 | ||
| Sun, Sep 27 | 50–53 | 11 | ||
| Mon, Sep 28 | 53–56 | 12 | ||
| Tue, Sep 29 | 56–56 | 12 | ||
| Wed, Sep 30 | 56–57 | 12 |
Common questions about the air in San Francisco
Is the air in San Francisco safe today?
Yes. Right now the US AQI in San Francisco is 44, which counts as good. Great air. A perfect time to be outside. It is expected to reach 53 (moderate) around Sun 4:00 PM.
When is the best time to be outside in San Francisco?
Sat 5:00 PM–8:00 PM. That is the cleanest stretch in the next 24 hours, with the US AQI averaging about 45. The worst hour is around Sun 4:00 PM, at 53.
What is the main pollutant in San Francisco?
Fine particles (PM2.5). It drives the index right now, at 9.9 µg/m³. Tiny particles from combustion, fires and dust that reach deep into the lungs. The main driver of AQI worldwide.
How does San Francisco's air compare with the WHO guideline?
Within the guideline. Over the next 24 hours PM2.5 averages about 10 µg/m³, against the World Health Organization's 24-hour guideline of 15 µg/m³. The other pollutants stay within their guideline levels.
How many cigarettes is a day of San Francisco's air?
About 0.5 cigarettes. Over the next 24 hours PM2.5 averages about 10 µg/m³. By Berkeley Earth's rule of thumb, 22 µg/m³ breathed for a day is roughly one cigarette.
Will air quality in San Francisco improve this week?
Today looks cleanest. Its AQI peaks at 50, against 57 on Wednesday, the worst day in the forecast.
Measured near San Francisco
| Station | PM2.5 µg/m³ | Measured |
|---|---|---|
| San Francisco AirNow, reference monitor | 5.0 | Sat 3:00 PM |
| Oakland West AirNow, reference monitor | 8.0 | Sat 3:00 PM |
| Berkeley Aquatic Park AirNow, reference monitor | 10 | Sat 3:00 PM |
Air quality near San Francisco
- Sacramento 121 km NE
- Fresno 260 km SE
- Los Angeles 559 km SE
- Las Vegas 671 km E
- San Diego 738 km SE
- Portland 861 km N
About this forecast
Forecast from CAMS global via Open-Meteo: the Copernicus Atmosphere Monitoring Service (CAMS) model at about 40 km resolution (10 km inside Europe), refreshed twice a day. Models smooth out street-level peaks, so busy roads and industrial sites can be worse than shown; ground stations, where there are any nearby, show what monitors actually measure. The US AQI follows the US EPA scale and the European AQI the EEA bands. Readings for 37.77°N, 122.42°W, updated 2026-09-27 00:00 UTC.