California · AirNow reporting area
San Francisco, CA air quality
The Air Quality Index in San Francisco is 20 (Good) as of 3:00 AM PDT on Wed, Oct 28, with Fine particles (PM2.5) as the main pollutant. Today's forecast: AQI 55, Moderate (PM2.5). Tomorrow: Moderate (PM2.5). Preliminary data from the EPA AirNow program, reported by Bay Area Air District.
Current AQI
AQI now
20Good3:00 AM PDT, Wed, Oct 28
By pollutant
- PM2.5: 20Good
- Ozone: 12Good
Yesterday's highest AQI
24GoodOzone, Tue, Oct 27
What this AQI means for your health
Good (AQI 0–50). Air pollution is low and is not expected to affect health. A good day to be active outside.
These are general guidelines based on EPA's AQI categories, written in our own words. See the full AQI scale.
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Air quality forecast
Daily AQI forecast issued by Bay Area Air District. Some areas forecast a category without a number.
| Day | Forecast | Pollutants |
|---|---|---|
| Today, Wed, Oct 28 | 55Moderate | PM2.5 55 |
| Tomorrow, Thu, Oct 29 | Moderate | PM2.5 Moderate |
| Fri, Oct 30 | Moderate | PM2.5 Moderate |
| Sat, Oct 31 | Moderate | PM2.5 Moderate |
Monitor readings
Latest hourly NowCast AQI at 1 monitor assigned to or near this area. NowCast weighs recent hours more heavily so it reacts faster to changes. Distance is from the area's center point.
| Monitor | Hour | PM2.5 AQI | Ozone AQI | PM10 AQI | PM2.5 µg/m³ | Miles |
|---|---|---|---|---|---|---|
| San Francisco | 2 AM | 16 | 9 | — | 2 | 2 |
Last 12 hours
Highest hourly NowCast AQI among the monitors above, for each hour (PDT).
| Hour starting | PM2.5 AQI | Ozone AQI | PM10 AQI | Monitors |
|---|---|---|---|---|
| 2 AM | 16 | 9 | — | 1 |
| 1 AM | 20 | 12 | — | 1 |
| 12 AM | 29 | 13 | — | 1 |
| 11 PM | 30 | 15 | — | 1 |
| 10 PM | 21 | 17 | — | 1 |
| 9 PM | 20 | 19 | — | 1 |
| 8 PM | 24 | 21 | — | 1 |
| 7 PM | 21 | 23 | — | 1 |
| 6 PM | 19 | 24 | — | 1 |
| 5 PM | 27 | 26 | — | 1 |
| 4 PM | 33 | 25 | — | 1 |
| 3 PM | 27 | 25 | — | 1 |
Hourly monitor values from AirNow HourlyAQObs files, latest hour Oct 28, 2026, 5:00 AM EDT. Single-hour readings can be missing or revised.
Protecting yourself on bad air days
When the AQI is high, spend less time being active outdoors, keep windows closed if the outdoor air is worse than indoors, and run a portable HEPA air cleaner or your central system with a high-efficiency filter (MERV 13 or higher if your system can handle it). When fine particles or smoke are the problem, a well-fitted N95 respirator gives much better protection than a cloth or surgical mask. Read more on our wildfire smoke page.
Shopping for an air cleaner? Compare air purifiers on OpenPicks, our sister site.
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Sources
- Current AQI, yesterday's maximum and forecasts: U.S. EPA AirNow reporting area file (files.airnowtech.org), as of Oct 28, 2026, 6:12 AM EDT.
- Monitor readings: AirNow HourlyAQObs files (hourly NowCast AQI and raw concentrations).
- Reporting agencies: Bay Area Air District. These agencies own the data and are the authority for forecasts and advisories.
- Values are shown as received from AirNow. See AirNow partners for the full list of agencies.
Preliminary data. AirNow readings and forecasts come from federal, state, local and tribal air quality agencies. They are not fully verified, may change, and must not be used for regulatory or official decisions; official data are in EPA's Air Quality System. For the latest official readings and advisories, check AirNow.gov and your state or local air agency.
This page is general information, not medical advice. If you have symptoms or a health condition, follow your doctor's guidance.
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