Old San Juan, San Juan Air Quality Forecast - Today, Tomorrow
Air Quality Today
Today (6 October): Air quality in Old San Juan is very poor. AQI, PM2.5, and PM10 are very poor; NO2, O3, SO2, CO, HCHO, and PM1 are good. Pollution peaks around 8:00 AM (PM10: 100/100).
Air Quality Tomorrow
Tomorrow (7 October 2026): Air quality in Old San Juan is very poor. All pollutants stay as today. Pollution peaks around 12:00 AM (PM10: 100/100).
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Air Quality
Today - 6 October
| Pollen species | Level | Value |
|---|---|---|
| AQI | Very poor | 100/100 |
| PM2.5 (fine particles) | Very poor | 85.3/100 |
| PM10 (coarse particles) | Very poor | 100/100 |
| NO2 (nitrogen dioxide) | Good | 0.2/100 |
| O3 (ozone) | Good | 10.8/100 |
| SO2 (sulfur dioxide) | Good | 0.2/100 |
| CO (carbon monoxide) | Good | 0.4/100 |
| HCHO (formaldehyde) | Good | 0.7/100 |
| PM1 (ultrafine particles) | Good | 17.9/100 |
Tomorrow - 7 October
| Pollen species | Level | Value |
|---|---|---|
| AQI | Very poor | 100/100 |
| PM2.5 (fine particles) | Very poor | 83.0/100 |
| PM10 (coarse particles) | Very poor | 100/100 |
| NO2 (nitrogen dioxide) | Good | 0.2/100 |
| O3 (ozone) | Good | 11.5/100 |
| SO2 (sulfur dioxide) | Good | 0.3/100 |
| CO (carbon monoxide) | Good | 0.4/100 |
| HCHO (formaldehyde) | Good | 0.6/100 |
| PM1 (ultrafine particles) | Good | 19.4/100 |
Local Environmental Conditions
With buildings covering much of the area around this location in San Juan, traffic and other urban emissions are the biggest local influence on air quality. Breezes off the Atlantic Ocean usually help ventilate the area. Parks and street trees provide a modest buffer against traffic pollution. Pollution carried in from the wider region can also raise levels at times.
The dry season, roughly December to March, brings the haziest air, as dust and smoke build up without rain to clear them. Heavy rains from September to November clear the air most effectively. With temperatures around 27°C all year, sunny afternoons can raise ozone levels in any month, especially near busy roads.
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Frequently Asked Questions About Air Quality in Puerto Rico
Is air quality bad in Old San Juan right now?
On 6 October 2026, overall air quality in Old San Juan is very poor. AQI is the main air quality indicator at 100/100. Pollution peaks around 8:00 AM (PM10: 100/100).
Will air quality be worse tomorrow in Old San Juan?
On 7 October 2026, air quality conditions in Old San Juan will be similar to today, with AQI forecast at very poor at 100/100. Pollution peaks around 12:00 AM (PM10: 100/100).
When is air pollution at its worst in Old San Juan?
The dry season, roughly December to March, brings the haziest air, as dust and smoke build up without rain to clear them. Heavy rains from September to November clear the air most effectively. With temperatures around 27°C all year, sunny afternoons can raise ozone levels in any month, especially near busy roads.
Are air quality levels in Old San Juan 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. |