Air quality
Air quality in San José, Alajuela Province today
Updated
Good (US AQI 29) Air quality is satisfactory and poses little or no risk; a good time for outdoor activity. Model estimate for Sun, Oct 25, 2:00 pm (20:00 UTC).
Live AQI, PM2.5, PM10 and ozone for San José, Alajuela Province, Costa Rica, with a 48-hour forecast and the best time to be outside.
- US AQI now
- 29 Good
- PM2.5
- 5.1 µg/m³ 0.3× WHO 24-h guideline
- PM10
- 7 µg/m³
- Ozone
- 68 µg/m³
- Dominant pollutant
- PM2.5 sub-index 29
- Best hour today
- 2:00 pm AQI 29
- European AQI
- 24
Air quality in San José, Alajuela Province right now
Right now the modelled US Air Quality Index for San José, Alajuela Province, Costa Rica is 29, which falls in the "Good" band (up to 50). Air quality is satisfactory and poses little or no risk; a good time for outdoor activity.
The index is driven mainly by PM2.5, whose own sub-index is 29. 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 5.1 µg/m³, within the WHO 24-hour guideline of 15 µg/m³; PM10 is 7 µg/m³ against a guideline of 45; ozone is 68 µg/m³ (below the WHO 8-hour level of 100); nitrogen dioxide is 0.1 µg/m³ (below the 24-hour guideline of 25).
Also this hour: UV index 3.3, carbon monoxide 113 µg/m³.
NASA FIRMS shows 6 fire hotspots within 300 km in the last day (nearest about 48 km), but particle levels are not elevated enough to point to smoke right now.
San José, Alajuela Province AQI forecast: next 48 hours
Over the next 24 hours the AQI is forecast to range from 28 around Sun 10:00 pm to 31 around Sun 4:00 pm, staying "Good" throughout.
The following day looks similar, averaging about 27.
| Local time (America/Costa_Rica) | US AQI | Category | PM2.5 µg/m³ | PM10 µg/m³ | Ozone µg/m³ |
|---|---|---|---|---|---|
| Sun 2:00 pm | 29 | Good | 5.1 | 7 | 68 |
| Sun 5:00 pm | 31 | Good | 5.8 | 8 | 47 |
| Sun 8:00 pm | 29 | Good | 6.6 | 8 | 35 |
| Sun 11:00 pm | 28 | Good | 6.2 | 7 | 29 |
| Mon 2:00 am | 28 | Good | 5.2 | 6 | 29 |
| Mon 5:00 am | 29 | Good | 4.5 | 6 | 33 |
| Mon 8:00 am | 30 | Good | 4.6 | 6 | 61 |
| Mon 11:00 am | 29 | Good | 3.5 | 5 | 75 |
| Mon 2:00 pm | 30 | Good | 3.2 | 4 | 73 |
| Mon 5:00 pm | 33 | Good | 3.7 | 5 | 52 |
| Mon 8:00 pm | 28 | Good | 5.1 | 6 | 35 |
| Mon 11:00 pm | 25 | Good | 5.2 | 6 | 29 |
| Tue 2:00 am | 24 | Good | 4.9 | 6 | 29 |
| Tue 5:00 am | 24 | Good | 4.9 | 6 | 29 |
| Tue 8:00 am | 24 | Good | 4.7 | 7 | 63 |
| Tue 11:00 am | 25 | Good | 4.2 | 6 | 75 |
| Tue 2:00 pm | 30 | Good | 3.7 | 5 | 73 |
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 José, Alajuela Province today
Between 6 am and 9 pm local time, the cleanest air today is forecast around 2:00 pm (AQI 29, Good) and the worst around 4:00 pm (AQI 31). The difference across the day is small, so timing matters little.
San José, Alajuela Province vs the rest of Costa Rica
Across 5 Costa Rica cities we track, the average US AQI right now is 37 (Good). San José, Alajuela Province at 29 is 8 points cleaner than average.
For context, the median across 3,556 cities worldwide is 58.
Air quality in cities near San José, Alajuela Province
| City | Distance | US AQI | Category | PM2.5 µg/m³ |
|---|---|---|---|---|
| Liberia | 48 km | 30 | Good | 4.8 |
| Granada, Granada Department | 141 km | 37 | Good | 6.8 |
| Masaya | 154 km | 37 | Good | 6.8 |
| San Pablo, Heredia Province | 156 km | 39 | Good | 3.6 |
| San Juan, San José | 160 km | 39 | Good | 3.6 |
| San José, San José | 161 km | 39 | Good | 3.6 |
| San Pedro, San José | 164 km | 39 | Good | 3.6 |
| Managua | 179 km | 44 | Good | 7.8 |
Model vs measured
We found no measured PM2.5 sensor cell within 25 km of San José, Alajuela Province, 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
With the AQI at 29, there is no need for sensitive groups to change plans. People with asthma should still carry their reliever inhaler as usual.
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 José
Air quality elsewhere
Data: Open-Meteo Air Quality API, Copernicus Atmosphere Monitoring Service (CAMS), NASA FIRMS.