Air quality in San Marcos, Texas, United States of America today
Mr. Duck’s Air Quality Score
Good air today for San Marcos, Ancash, Peru
This friendly indicator summarizes the latest city readings. For health guidance, please see: EPA AirNow or WHO.
Air quality today
The air quality in San Marcos, Texas is classified as Good today. The primary pollutant identified is PM2.5 (fine particles).
Measurements show a PM2.5 concentration of 4.3 µg/m³ based on six valid observations reported through OpenAQ. No PM10 value is available for this assessment. This page is informational; for health guidance, use official sources such as EPA AirNow or WHO.
Latest sensor values
PM categories follow US EPA AQI breakpoints, shown here as an estimate derived from the latest valid measurements (this project does not compute EPA NowCast/24-hour AQI yet).
What the data includes
The air‑quality record for San Marcos, Texas includes data on two pollutants: ozone (O3) and fine particulate matter (PM2.5). Both measurements come from a single monitoring site, the San Marcos Staples R station, which supplies two rows of data—one row per pollutant.
For ozone, the only available value is 0.015 ppm recorded at the Staples R location on 2025‑11‑19 16:00 UTC. This timestamp is more than a year old, indicating that the ozone reading reflects conditions from well before the current reporting period and there have been no newer observations for this pollutant. In contrast, the PM2.5 measurement is much fresher: a concentration of 4.3 µg/m³ was logged at the same station on 2026‑02‑11 00:00 UTC, just one week ago.
Both pollutants show identical minimum, median and maximum values across their respective rows, meaning each dataset contains a single observation rather than a range of measurements. Consequently, there is no spread to describe variability; the reported figures represent the sole recent reading for each contaminant at this site. Because only one monitoring location contributes data, spatial coverage within San Marcos is limited—conditions elsewhere in the city may differ from those captured at Staples R.
Overall, the dataset provides a very narrow snapshot: ozone information is outdated, while PM2.5 is up‑to‑date but still based on a single point measurement. Users should keep in mind that air quality can change across neighborhoods and over time, and the current data set does not capture those variations.
Learn more about sources and filtering: About the data.
Trusted references: WHO (Air pollution) · US EPA AirNow · European Environment Agency (Air)
Latest sensor values (bars)
PM categories follow US EPA AQI breakpoints, shown here as an estimate derived from the latest valid measurements (this project does not compute EPA NowCast/24-hour AQI yet).
Data notes
The data shown reflects six valid measurements and is Updated today (last refreshed at 2026‑02‑11T00:00:00+00:00). These readings provide a snapshot of current conditions, but air quality can vary by location and time within San Marcos, Texas, so values may differ across neighborhoods or later in the day.
OpenAQ station rows
| Station | Parameter | Value | Unit | Last updated |
|---|---|---|---|---|
| San Marcos Staples R | o3 | 0.015 | ppm | 2025-11-19 16:00 UTC |
| San Marcos Staples R | pm25 | 4.3 | µg/m³ | 2026-02-11 00:00 UTC |