Worst air pollution San Cristóbal, today and tomorrow
Today (20 September): Air quality in San Cristóbal is very poor. AQI and PM10 are very poor; PM2.5 is poor; PM1 is fair; NO2, O3, SO2, CO, and HCHO are good. Pollution peaks around 12:00 AM (PM10: 100/100).
Tomorrow (21 September 2026): Air quality in San Cristóbal is very poor. PM2.5 increases to very poor; PM1 increases to moderate; all other pollutants stay as today. Pollution peaks around 5:00 PM (PM10: 100/100). Airmine updates local air quality forecasts four times daily.
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Developed with support from the European Space Agency (ESA)’s Business Applications and Space Solutions (BASS) team
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San Cristóbal's air quality reflects the Chiapas Highland's Los Altos enclosed basin at 2,176 metres surrounded by the Altos de Chiapas ranges, with vehicle traffic on surrounding roads and the tourism, indigenous crafts, and government corridor contributing local sources. The basin's near-complete mountain enclosure creates severe concentration under winter inversions, while the elevated altitude worsens ozone formation and the wood-burning residential heating in this indigenous highland community generates elevated winter PM2.5 throughout the year.
Today - 20 September | Pollution peaks at 00:00
AQI:
Very poor
100/100
PM2.5 (fine particles):
Poor
78.9/100
PM10 (coarse particles):
Very poor
100/100
NO2 (nitrogen dioxide):
Good
5.9/100
O3 (ozone):
Good
14.8/100
SO2 (sulfur dioxide):
Good
0.3/100
CO (carbon monoxide):
Good
0.5/100
HCHO (formaldehyde):
Good
3.4/100
PM1 (ultrafine particles):
Fair
37.2/100
Levels show the poorest local air quality during the day
Tomorrow - 21 September | Pollution peaks at 17:00
AQI:
Very poor
100/100
PM2.5 (fine particles):
Very poor
99.1/100
PM10 (coarse particles):
Very poor
100/100
NO2 (nitrogen dioxide):
Good
8.3/100
O3 (ozone):
Good
15.9/100
SO2 (sulfur dioxide):
Good
0.4/100
CO (carbon monoxide):
Good
0.5/100
HCHO (formaldehyde):
Good
3.5/100
PM1 (ultrafine particles):
Moderate
44.5/100
Frequently Asked Questions
Is air quality bad in San Cristóbal right now?
On 20 September 2026, overall air quality in San Cristóbal is very poor. AQI is the main air quality indicator at 100/100. Pollution peaks around 12:00 AM (PM10: 100/100).
Will air quality be worse tomorrow in San Cristóbal?
On 21 September 2026, air quality conditions in San Cristóbal will be similar to today, with AQI forecast at very poor at 100/100. Pollution peaks around 5:00 PM (PM10: 100/100).
When is air pollution at its worst in San Cristóbal?
In San Cristóbal, traffic on the surrounding roads, charcoal and wood-burning, together with seasonal tourism traffic are the main local sources, with conditions worsening when calm, stagnant conditions settle in the surrounding valley. Topographic enclosure in the valley lets pollution accumulate rather than clear out. Photochemical reactions in the heat push ozone levels higher.
Are air quality levels in San Cristóbal 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.
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Data provided by Airmine — Last update: 21 September 2026 at 03:04 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.
Disclaimer: Forecasts are provided for informational purposes only and should not be relied upon as medical advice. Actual pollen and air quality conditions may vary from the forecast. If you have allergies, asthma, or another medical condition, consult a healthcare professional. Please see our Terms of Service for important information about limitations of liability.
Some text on this page may be generated or summarised using artificial intelligence (AI). Wherever possible, AI-generated content is enriched with Airmine's proprietary data to improve its accuracy and relevance. However, AI-generated content may still contain errors, omissions, or inaccuracies.
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