San Francisco Air Quality Forecast - Today, Tomorrow
Air Quality Today
Today (10 October): Air quality in San Francisco is moderate. AQI and O3 are moderate; PM2.5, PM10, NO2, SO2, CO, HCHO, and PM1 are good. Pollution peaks around 2:00 AM (O3: 42.1/100).
Air Quality Tomorrow
Tomorrow (11 October 2026): Air quality in San Francisco is moderate. PM2.5 increases to fair; all other pollutants stay as today. Pollution peaks around 11:00 PM (O3: 43.8/100).
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Air Quality
Today - 10 October
| Pollutant | Level | Value |
|---|---|---|
| AQI | Moderate | 42.1/100 |
| PM2.5 (fine particles) | Good | 15.1/100 |
| PM10 (coarse particles) | Good | 13.0/100 |
| NO2 (nitrogen dioxide) | Good | 1.4/100 |
| O3 (ozone) | Moderate | 42.1/100 |
| SO2 (sulfur dioxide) | Good | 0.5/100 |
| CO (carbon monoxide) | Good | 0.5/100 |
| HCHO (formaldehyde) | Good | 1.5/100 |
| PM1 (ultrafine particles) | Good | 3.8/100 |
Tomorrow - 11 October
| Pollutant | Level | Value |
|---|---|---|
| AQI | Moderate | 43.8/100 |
| PM2.5 (fine particles) | Fair | 23.5/100 |
| PM10 (coarse particles) | Good | 19.9/100 |
| NO2 (nitrogen dioxide) | Good | 3.3/100 |
| O3 (ozone) | Moderate | 43.8/100 |
| SO2 (sulfur dioxide) | Good | 0.8/100 |
| CO (carbon monoxide) | Good | 0.5/100 |
| HCHO (formaldehyde) | Good | 2.5/100 |
| PM1 (ultrafine particles) | Good | 7.2/100 |
Local Environmental Conditions
With buildings covering much of the area around the heart of San Francisco, traffic and other urban emissions are the biggest local influence on air quality. Breezes off the Pacific Ocean usually help ventilate the area. Parks and street trees provide a modest buffer against traffic pollution. On some days, pollution drifting in from farther away outweighs local sources.
Air near roads is often at its worst from January to March, when nights cool to around 11°C and the air turns still. Ozone rises a little on sunny days from August to September, but the mild summers, around 17°C, keep it in check. Breezy weather in May, with winds near 20 km/h, tends to sweep pollution away.
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Frequently Asked Questions About Air Quality in California
Is air quality bad in San Francisco right now?
On 10 October 2026, overall air quality in San Francisco is moderate. AQI is the main air quality indicator at 42.1/100. Pollution peaks around 2:00 AM (O3: 42.1/100).
Will air quality be worse tomorrow in San Francisco?
On 11 October 2026, air quality conditions in San Francisco will be similar to today, with AQI forecast at moderate at 43.8/100. Pollution peaks around 11:00 PM (O3: 43.8/100).
When is air pollution at its worst in San Francisco?
Air near roads is often at its worst from January to March, when nights cool to around 11°C and the air turns still. Ozone rises a little on sunny days from August to September, but the mild summers, around 17°C, keep it in check. Breezy weather in May, with winds near 20 km/h, tends to sweep pollution away.
Are air quality levels in San Francisco based on measurements or forecasts?
It is forecasts derived by downscaling forecasts provided by EU’s Copernicus Atmosphere Monitoring Service (CAMS) by taking into account local conditions such as traffic patterns. CAMS bases its forecast on satellite measurements of particles and chemical compounds in the atmosphere. Airmine’s services were developed with support from the European Space Agency (ESA)’s Business Applications and Space Solutions (BASS) team.
Why doesn’t the forecast always reflect wildfire impacts?
Airmine’s forecast uses CAMS (Copernicus Atmosphere Monitoring Service) as its background atmospheric model. While CAMS includes wildfire emissions, these are derived from satellite observations and are not available in real time. During rapidly evolving wildfire events, there may therefore be a delay before increased emissions are incorporated into the model. As a result, the forecast may temporarily underestimate PM₂.₅ and other pollutants associated with wildfire smoke.
During rapidly evolving wildfire events, CAMS may lag by approximately 1–2 days before increased wildfire emissions are fully represented, which can lead to temporary underestimation of PM₂.₅ concentrations in Airmine’s forecast.
Understanding the Scale
The 0–100 air quality scores represent risk levels, not direct air pollutant concentrations. Higher scores indicate higher risk.
Air Quality
| Good | 0-20 | Low air quality risk. Air quality is expected to be good, with low levels of pollution. |
| Fair | 20-40 | Generally low air quality risk. Air quality is expected to be acceptable, with some pollution present. |
| Moderate | 40-60 | Moderate air quality risk. Air pollution is elevated and air quality may be less favorable. |
| Poor | 60-80 | High air quality risk. Air pollution is high and air quality is expected to be poor. |
| Very Poor | 80-100 | Very high air quality risk. Air pollution is very high and air quality is expected to be very poor. |