Worst air pollution San Marcos, today and tomorrow
Today (16 July): Air quality in San Marcos is fair. AQI, PM2.5, PM10, and O3 are fair; NO2, SO2, CO, HCHO, and PM1 are good. Pollution peaks around 12:00 PM (PM10: 35.5/100).
Tomorrow (17 July 2026): Air quality in San Marcos is fair. All pollutants stay as today. Pollution peaks around 12:00 PM (O3: 26.5/100). 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 Marcos' air quality reflects its position along the I-35 corridor between Austin and San Antonio, with vehicle emissions from the interstate and Texas State University campus traffic contributing local sources. The San Marcos River and surrounding Hill Country provide some natural ventilation, while summer ozone from the broader Austin-San Antonio regional corridor is the primary warm-season concern throughout the year.
Today - 16 July | Pollution peaks at 12:00
AQI:
Fair
35.5/100
PM2.5 (fine particles):
Fair
25.3/100
PM10 (coarse particles):
Fair
35.5/100
NO2 (nitrogen dioxide):
Good
0.3/100
O3 (ozone):
Fair
29.8/100
SO2 (sulfur dioxide):
Good
6.7/100
CO (carbon monoxide):
Good
0.0/100
HCHO (formaldehyde):
Good
0.8/100
PM1 (ultrafine particles):
Good
5.3/100
Levels show the poorest local air quality during the day
Tomorrow - 17 July | Pollution peaks at 12:00
AQI:
Fair
26.5/100
PM2.5 (fine particles):
Fair
20.9/100
PM10 (coarse particles):
Fair
21.0/100
NO2 (nitrogen dioxide):
Good
0.2/100
O3 (ozone):
Fair
26.5/100
SO2 (sulfur dioxide):
Good
6.1/100
CO (carbon monoxide):
Good
0.0/100
HCHO (formaldehyde):
Good
0.8/100
PM1 (ultrafine particles):
Good
4.6/100
Pollen forecast in San Marcos
View pollen forecastFrequently Asked Questions
Is air quality bad in San Marcos right now?
On 16 July 2026, overall air quality in San Marcos is fair. AQI is the main air quality indicator at 35.5/100. Pollution peaks around 12:00 PM (PM10: 35.5/100).
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 fair at 26.5/100. Pollution peaks around 12:00 PM (O3: 26.5/100).
When is air pollution at its worst in San Marcos?
Conditions in San Marcos vary noticeably across the seasons. Typically, spring and autumn generally bring more moderate, cleaner conditions between the extremes of summer and winter cedar season, while extended summer heat waves bring the year's worst ozone readings in the state's biggest metro areas. Gulf Coast humidity and inland heat can each add their own seasonal pollution patterns.
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