Air quality
Air quality in San Jose today
Updated
Moderate (US AQI 52) Acceptable for most people. Unusually sensitive people should consider shortening long or heavy exertion outdoors. Model estimate for Sun, Oct 25, 5:00 pm (00:00 UTC).
Live AQI, PM2.5, PM10 and ozone for San Jose, California, United States, with a 48-hour forecast and the best time to be outside.
- US AQI now
- 52 Moderate
- PM2.5
- 7.4 µg/m³ 0.5× WHO 24-h guideline
- PM10
- 8.6 µg/m³
- Ozone
- 99 µg/m³
- Dominant pollutant
- PM2.5 sub-index 52
- Best hour today
- 5:00 pm AQI 52
- European AQI
- 40
Air quality in San Jose right now
Right now the modelled US Air Quality Index for San Jose, California, United States is 52, which falls in the "Moderate" band (up to 100). Acceptable for most people. Unusually sensitive people should consider shortening long or heavy exertion outdoors.
The index is driven mainly by PM2.5, whose own sub-index is 52. Fine and coarse particles come from traffic, heating, industry, dust and smoke; they build up on calm nights and clear when wind or rain arrives.
PM2.5 is 7.4 µg/m³, within the WHO 24-hour guideline of 15 µg/m³; PM10 is 8.6 µg/m³ against a guideline of 45; ozone is 99 µg/m³ (below the WHO 8-hour level of 100); nitrogen dioxide is 4.7 µg/m³ (below the 24-hour guideline of 25).
Also this hour: carbon monoxide 189 µg/m³.
San Jose AQI forecast: next 48 hours
Over the next 24 hours the AQI is forecast to range from 52 around Sun 5:00 pm to 73 around Mon 2:00 pm, staying "Moderate" throughout.
The following day is expected to be cleaner, averaging about 58 against 63 for the next 24 hours.
| Local time (America/Los_Angeles) | US AQI | Category | PM2.5 µg/m³ | PM10 µg/m³ | Ozone µg/m³ |
|---|---|---|---|---|---|
| Sun 5:00 pm | 52 | Moderate | 7.4 | 9 | 99 |
| Sun 8:00 pm | 54 | Moderate | 16 | 18 | 44 |
| Sun 11:00 pm | 55 | Moderate | 25.4 | 28 | 30 |
| Mon 2:00 am | 58 | Moderate | 34.2 | 38 | 17 |
| Mon 5:00 am | 63 | Moderate | 39.8 | 43 | 19 |
| Mon 8:00 am | 68 | Moderate | 31.3 | 36 | 18 |
| Mon 11:00 am | 72 | Moderate | 10.9 | 15 | 75 |
| Mon 2:00 pm | 73 | Moderate | 7.5 | 11 | 87 |
| Mon 5:00 pm | 73 | Moderate | 6.2 | 9 | 79 |
| Mon 8:00 pm | 72 | Moderate | 4.6 | 6 | 60 |
| Mon 11:00 pm | 69 | Moderate | 6.4 | 8 | 48 |
| Tue 2:00 am | 64 | Moderate | 7.4 | 10 | 47 |
| Tue 5:00 am | 57 | Moderate | 8.7 | 12 | 52 |
| Tue 8:00 am | 51 | Moderate | 10.8 | 14 | 50 |
| Tue 11:00 am | 43 | Good | 9.3 | 14 | 79 |
| Tue 2:00 pm | 43 | Good | 9.8 | 14 | 87 |
| Tue 5:00 pm | 45 | Good | 10.3 | 15 | 85 |
Every third hour of the CAMS forecast via Open-Meteo. US AQI uses rolling averages (24 h for particles, 8 h for ozone), so it moves more slowly than the hourly concentrations.
Best time to be outside in San Jose today
Between 6 am and 9 pm local time, the cleanest air today is forecast around 5:00 pm (AQI 52, Moderate) and the worst around 8:00 pm (AQI 54). The difference across the day is small, so timing matters little.
San Jose vs the rest of United States
Across 619 United States cities we track, the average US AQI right now is 52 (Moderate). San Jose at 52 is about average.
It ranks 368 of 619 from cleanest to most polluted; the cleanest is Hilo (20) and the most polluted Springfield, PA (133).
For context, the median across 3,556 cities worldwide is 58.
Air quality in cities near San Jose
| City | Distance | US AQI | Category | PM2.5 µg/m³ |
|---|---|---|---|---|
| Santa Clara, CA | 6 km | 54 | Moderate | 8.5 |
| Sunnyvale | 13 km | 54 | Moderate | 8.5 |
| Fremont | 25 km | 60 | Moderate | 17.2 |
| Newark, CA | 25 km | 60 | Moderate | 17.2 |
| Union City | 31 km | 60 | Moderate | 17.2 |
| Hayward | 40 km | 60 | Moderate | 17.2 |
| Dublin, CA | 41 km | 60 | Moderate | 17.2 |
| Ashland | 44 km | 60 | Moderate | 17.2 |
Model vs measured
The nearest measured PM2.5 reading is 3.7 µg/m³ from Sensor.Community (median of 3 sensors), centred about 17 km from the city centre. That is 3.7 µg/m³ below the model estimate of 7.4 µg/m³. Low-cost sensors can read high in humid air; reference monitors are more accurate but sparser.
Wildfire smoke
PM2.5 is forecast to reach 40 µg/m³ in the next 24 hours while NASA satellites detected 29 fire hotspots within 300 km in the last day (nearest about 13 km away). Smoke is a likely contributor: keep windows closed, run an air purifier or HVAC filter, and check the fire map before heading out.
Advice for sensitive groups
At 52, most people are fine outdoors. If you are unusually sensitive to PM2.5, keep long or intense workouts to the cleaner hours shown above.
What the US AQI numbers mean
| US AQI | Category | What it means |
|---|---|---|
| 0-50 | Good | Air quality is satisfactory and poses little or no risk; a good time for outdoor activity. |
| 51-100 | Moderate | Acceptable for most people. Unusually sensitive people should consider shortening long or heavy exertion outdoors. |
| 101-150 | Unhealthy for Sensitive Groups | People with heart or lung disease, older adults, children and teens should cut back on prolonged or heavy exertion outdoors. |
| 151-200 | Unhealthy | Everyone should reduce prolonged or heavy exertion outdoors; sensitive groups should avoid it and keep windows closed. |
| 201-300 | Very Unhealthy | Health alert: everyone should avoid prolonged or heavy exertion outdoors, and sensitive groups should stay indoors. |
| 301-500 | Hazardous | Emergency conditions: everyone should avoid all outdoor physical activity and stay indoors with filtered air if possible. The scale tops out at 500; heavier dust or smoke is shown as 500. |
Values on this page are modelled by CAMS (Copernicus) and served by Open-Meteo; they are estimates for the area around the city centre, not readings from an official monitor.
Nearby cities
More for San Jose
Air quality elsewhere
Data: Open-Meteo Air Quality API, Copernicus Atmosphere Monitoring Service (CAMS), Sensor.Community, NASA FIRMS.