Air quality
Air quality in Belmont today
Updated
Moderate (US AQI 58) Acceptable for most people. Unusually sensitive people should consider shortening long or heavy exertion outdoors. Model estimate for Sun, Oct 25, 1:00 pm (20:00 UTC).
Live AQI, PM2.5, PM10 and ozone for Belmont, California, United States, with a 48-hour forecast and the best time to be outside.
- US AQI now
- 58 Moderate
- PM2.5
- 17 µg/m³ 1.1× WHO 24-h guideline
- PM10
- 18 µg/m³
- Ozone
- 45 µg/m³
- Dominant pollutant
- PM2.5 sub-index 58
- Best hour today
- 1:00 pm AQI 58
- European AQI
- 41
Air quality in Belmont right now
Right now the modelled US Air Quality Index for Belmont, California, United States is 58, 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 58. 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 17 µg/m³, 1.1 times the WHO 24-hour guideline of 15 µg/m³; PM10 is 18 µg/m³ against a guideline of 45; ozone is 45 µg/m³ (below the WHO 8-hour level of 100); nitrogen dioxide is 27 µg/m³ (above the 24-hour guideline of 25).
Also this hour: UV index 3.4, carbon monoxide 190 µg/m³.
NASA FIRMS shows 24 fire hotspots within 300 km in the last day (nearest about 31 km), but particle levels are not elevated enough to point to smoke right now.
Belmont AQI forecast: next 48 hours
Over the next 24 hours the AQI is forecast to range from 58 around Sun 1:00 pm to 62 around Sun 7:00 pm, staying "Moderate" throughout.
The following day is expected to be cleaner, averaging about 53 against 61 for the next 24 hours.
| Local time (America/Los_Angeles) | US AQI | Category | PM2.5 µg/m³ | PM10 µg/m³ | Ozone µg/m³ |
|---|---|---|---|---|---|
| Sun 1:00 pm | 58 | Moderate | 17.1 | 18 | 45 |
| Sun 4:00 pm | 60 | Moderate | 15.6 | 19 | 55 |
| Sun 7:00 pm | 62 | Moderate | 14 | 17 | 51 |
| Sun 10:00 pm | 62 | Moderate | 13.2 | 17 | 54 |
| Mon 1:00 am | 62 | Moderate | 12.8 | 17 | 57 |
| Mon 4:00 am | 61 | Moderate | 13.4 | 19 | 59 |
| Mon 7:00 am | 60 | Moderate | 12.6 | 18 | 57 |
| Mon 10:00 am | 59 | Moderate | 10.6 | 16 | 68 |
| Mon 1:00 pm | 58 | Moderate | 8.3 | 13 | 79 |
| Mon 4:00 pm | 56 | Moderate | 5.8 | 9 | 79 |
| Mon 7:00 pm | 54 | Moderate | 8.3 | 13 | 73 |
| Mon 10:00 pm | 53 | Moderate | 7.3 | 11 | 63 |
| Tue 1:00 am | 51 | Moderate | 8.2 | 12 | 61 |
| Tue 4:00 am | 50 | Good | 10.5 | 15 | 60 |
| Tue 7:00 am | 50 | Good | 12 | 17 | 59 |
| Tue 10:00 am | 50 | Good | 11.6 | 17 | 71 |
| Tue 1:00 pm | 50 | Good | 10.3 | 16 | 81 |
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 Belmont today
Between 6 am and 9 pm local time, the cleanest air today is forecast around 1:00 pm (AQI 58, Moderate) and the worst around 7:00 pm (AQI 62). The difference across the day is small, so timing matters little.
Belmont vs the rest of United States
Across 747 United States cities we track, the average US AQI right now is 49 (Good). Belmont at 58 is 9 points worse than average.
It ranks 574 of 747 from cleanest to most polluted; the cleanest is Aberdeen, SD (14) and the most polluted Springfield, PA (131).
For context, the median across 3,909 cities worldwide is 56.
Air quality in cities near Belmont
| City | Distance | US AQI | Category | PM2.5 µg/m³ |
|---|---|---|---|---|
| San Mateo, CA | 6 km | 58 | Moderate | 17.1 |
| Newark, CA | 21 km | 57 | Moderate | 10.3 |
| Hayward | 24 km | 57 | Moderate | 10.3 |
| Ashland | 24 km | 57 | Moderate | 10.3 |
| Union City | 24 km | 57 | Moderate | 10.3 |
| Fremont | 26 km | 57 | Moderate | 10.3 |
| Daly City | 26 km | 58 | Moderate | 17.1 |
| Sunnyvale | 27 km | 54 | Moderate | 5.7 |
Model vs measured
We found no measured PM2.5 sensor cell within 25 km of Belmont, so the numbers on this page are model estimates. Models capture regional pollution well but can miss very local sources such as a busy road or a nearby fire.
Advice for sensitive groups
At 58, 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 Belmont
Air quality elsewhere
Data: Open-Meteo Air Quality API, Copernicus Atmosphere Monitoring Service (CAMS), NASA FIRMS.