Worst air pollution San Marcos, today and tomorrow
Today (16 July): Air quality in San Marcos is good. AQI, PM2.5, PM10, NO2, O3, SO2, CO, HCHO, and PM1 are good. Pollution peaks around 9:00 AM (O3: 16.5/100).
Tomorrow (17 July 2026): Air quality in San Marcos is good. All pollutants stay as today. Pollution peaks around 10:00 AM (O3: 18.6/100). Airmine updates local air quality forecasts four times daily.
For long term forecasts and maps, see the Airmine app
Developed with support from the European Space Agency (ESA)’s Business Applications and Space Solutions (BASS) team
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San Marcos in Costa Rica reflects the flat Alajuela central plateau's San Marcos position at 900 metres, with vehicle traffic on surrounding roads and the coffee, agricultural, and residential corridor contributing local sources. The surrounding Costa Rican volcanic highlands create topographic variation, while the tropical climate's frequent convective rain provides effective atmospheric cleansing and San Marcos generally maintains moderate to good Costa Rican central plateau readings throughout most of the year.
Today - 16 July | Pollution peaks at 09:00
AQI:
Good
16.5/100
PM2.5 (fine particles):
Good
2.6/100
PM10 (coarse particles):
Good
0.8/100
NO2 (nitrogen dioxide):
Good
0/100
O3 (ozone):
Good
16.5/100
SO2 (sulfur dioxide):
Good
0/100
CO (carbon monoxide):
Good
0/100
HCHO (formaldehyde):
Good
9.1/100
PM1 (ultrafine particles):
Good
3.3/100
Levels show the poorest local air quality during the day
Tomorrow - 17 July | Pollution peaks at 10:00
AQI:
Good
18.6/100
PM2.5 (fine particles):
Good
3.3/100
PM10 (coarse particles):
Good
1.0/100
NO2 (nitrogen dioxide):
Good
0/100
O3 (ozone):
Good
18.6/100
SO2 (sulfur dioxide):
Good
0/100
CO (carbon monoxide):
Good
0/100
HCHO (formaldehyde):
Good
10.7/100
PM1 (ultrafine particles):
Good
4.5/100
Frequently Asked Questions
Is air quality bad in San Marcos right now?
On 16 July 2026, overall air quality in San Marcos is good. AQI is the main air quality indicator at 16.5/100. Pollution peaks around 9:00 AM (O3: 16.5/100).
Will air quality be worse tomorrow in San Marcos?
On 17 July 2026, air quality conditions in San Marcos will be similar to today, with AQI forecast at good at 18.6/100. Pollution peaks around 10:00 AM (O3: 18.6/100).
When is air pollution at its worst in San Marcos?
Air quality in San Marcos tends to be worse when vehicle traffic together with crop farming build up and still air allows pollutants to build up. Background emissions and local weather both shape how conditions change from day to day. Background emissions and local weather both play a role in day-to-day changes.
Are air quality levels in San Marcos 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.
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Data provided by Airmine — Last update: 16 July 2026 at 10:33 CEST (Data is updated four times daily.)
This forecast is produced independently using Airmine's own atmospheric data and models.
Unless explicitly made clear, the content on this site has not been paid for by external organisations and is Airmine's sole responsibility.
For long term forecasts and maps, see the Airmine app