Air quality
Air quality in San Marcos, TX today
Updated
Good (US AQI 50) Air quality is satisfactory and poses little or no risk; a good time for outdoor activity. Model estimate for Sun, Oct 25, 8:00 pm (01:00 UTC).
Live AQI, PM2.5, PM10 and ozone for San Marcos, Texas, United States, with a 48-hour forecast and the best time to be outside.
- US AQI now
- 50 Good
- PM2.5
- 8.9 µg/m³ 0.6× WHO 24-h guideline
- PM10
- 12 µg/m³
- Ozone
- 79 µg/m³
- Dominant pollutant
- PM2.5 sub-index 50
- Best hour tomorrow
- 12:00 pm AQI 45
- European AQI
- 30
Air quality in San Marcos, TX right now
Right now the modelled US Air Quality Index for San Marcos, Texas, United States is 50, which falls in the "Good" band (up to 50). Air quality is satisfactory and poses little or no risk; a good time for outdoor activity.
The index is driven mainly by PM2.5, whose own sub-index is 50. Fine and coarse particles come from traffic, heating, industry, dust and smoke; they build up on calm nights and clear when wind or rain arrives.
PM2.5 is 8.9 µg/m³, within the WHO 24-hour guideline of 15 µg/m³; PM10 is 12 µg/m³ against a guideline of 45; ozone is 79 µg/m³ (below the WHO 8-hour level of 100); nitrogen dioxide is 5.5 µg/m³ (below the 24-hour guideline of 25).
Also this hour: carbon monoxide 129 µg/m³.
NASA FIRMS shows 59 fire hotspots within 300 km in the last day (nearest about 32 km), but particle levels are not elevated enough to point to smoke right now.
San Marcos, TX AQI forecast: next 48 hours
Over the next 24 hours the AQI is forecast to range from 45 around Mon 12:00 pm to 52 around Mon 7:00 pm, from "Good" at best to "Moderate" at worst.
The following day looks similar, averaging about 51.
| Local time (America/Chicago) | US AQI | Category | PM2.5 µg/m³ | PM10 µg/m³ | Ozone µg/m³ |
|---|---|---|---|---|---|
| Sun 8:00 pm | 50 | Good | 8.9 | 12 | 79 |
| Sun 11:00 pm | 49 | Good | 7.3 | 9 | 74 |
| Mon 2:00 am | 48 | Good | 6 | 8 | 74 |
| Mon 5:00 am | 47 | Good | 6.8 | 9 | 69 |
| Mon 8:00 am | 46 | Good | 8.8 | 11 | 74 |
| Mon 11:00 am | 46 | Good | 9.1 | 12 | 99 |
| Mon 2:00 pm | 45 | Good | 9.4 | 13 | 119 |
| Mon 5:00 pm | 49 | Good | 8.7 | 12 | 105 |
| Mon 8:00 pm | 50 | Good | 11.4 | 14 | 80 |
| Mon 11:00 pm | 47 | Good | 10.6 | 13 | 72 |
| Tue 2:00 am | 50 | Good | 10 | 13 | 63 |
| Tue 5:00 am | 51 | Moderate | 10.6 | 14 | 53 |
| Tue 8:00 am | 52 | Moderate | 12.1 | 15 | 60 |
| Tue 11:00 am | 52 | Moderate | 9.5 | 13 | 89 |
| Tue 2:00 pm | 52 | Moderate | 8.5 | 12 | 107 |
| Tue 5:00 pm | 52 | Moderate | 8 | 11 | 93 |
| Tue 8:00 pm | 52 | Moderate | 8.7 | 12 | 74 |
Every third hour of the CAMS forecast via Open-Meteo. US AQI uses rolling averages (24 h for particles, 8 h for ozone), so it moves more slowly than the hourly concentrations.
Best time to be outside in San Marcos, TX tomorrow
Between 6 am and 9 pm local time, the cleanest air tomorrow is forecast around 12:00 pm (AQI 45, Good) and the worst around 7:00 pm (AQI 52). The difference across the day is small, so timing matters little.
San Marcos, TX vs the rest of United States
Across 619 United States cities we track, the average US AQI right now is 53 (Moderate). San Marcos, TX at 50 is about average.
For context, the median across 3,556 cities worldwide is 58.
Air quality in cities near San Marcos, TX
| City | Distance | US AQI | Category | PM2.5 µg/m³ |
|---|---|---|---|---|
| Austin | 47 km | 55 | Moderate | 10.2 |
| San Antonio | 74 km | 48 | Good | 8.4 |
| Georgetown, TX | 87 km | 62 | Moderate | 9.2 |
| Killeen | 139 km | 65 | Moderate | 8.9 |
| Temple | 147 km | 71 | Moderate | 8.2 |
| Victoria, TX | 150 km | 47 | Good | 5 |
| Bryan | 175 km | 62 | Moderate | 8.6 |
| College Station | 175 km | 62 | Moderate | 8.6 |
Model vs measured
We found no measured PM2.5 sensor cell within 25 km of San Marcos, TX, so the numbers on this page are model estimates. Models capture regional pollution well but can miss very local sources such as a busy road or a nearby fire.
Advice for sensitive groups
With the AQI at 50, there is no need for sensitive groups to change plans. People with asthma should still carry their reliever inhaler as usual.
What the US AQI numbers mean
| US AQI | Category | What it means |
|---|---|---|
| 0-50 | Good | Air quality is satisfactory and poses little or no risk; a good time for outdoor activity. |
| 51-100 | Moderate | Acceptable for most people. Unusually sensitive people should consider shortening long or heavy exertion outdoors. |
| 101-150 | Unhealthy for Sensitive Groups | People with heart or lung disease, older adults, children and teens should cut back on prolonged or heavy exertion outdoors. |
| 151-200 | Unhealthy | Everyone should reduce prolonged or heavy exertion outdoors; sensitive groups should avoid it and keep windows closed. |
| 201-300 | Very Unhealthy | Health alert: everyone should avoid prolonged or heavy exertion outdoors, and sensitive groups should stay indoors. |
| 301-500 | Hazardous | Emergency conditions: everyone should avoid all outdoor physical activity and stay indoors with filtered air if possible. The scale tops out at 500; heavier dust or smoke is shown as 500. |
Values on this page are modelled by CAMS (Copernicus) and served by Open-Meteo; they are estimates for the area around the city centre, not readings from an official monitor.
Nearby cities
More for San Marcos
Air quality elsewhere
Data: Open-Meteo Air Quality API, Copernicus Atmosphere Monitoring Service (CAMS), NASA FIRMS.