San Antonio Air Quality in September
Across 2019–2025, San Antonio's September air quality had a median AQI of 55 (Moderate) over 210 monitored days in the San Antonio-New Braunfels, TX area. 9.1% of September days (19 of 210) reached Unhealthy for Sensitive Groups or worse, and ground-level ozone set the daily AQI on 57.6% of days. The cleanest September on record here was 2019 (median AQI 52, 0 days above 100) and the worst was 2021 (median 71, 5 days above 100, peak AQI 147).
- Good: 32.9%
- Moderate: 58.1%
- Unhealthy for Sensitive Groups: 8.6%
- Unhealthy or worse: 0.5%
Extra Protection for San Antonio Homes
Air quality in San Antonio is moderate (AQI 52), with fine particles (PM2.5) the main concern. A True-HEPA purifier gives sensitive groups — kids, seniors and anyone with asthma or allergies — cleaner air indoors on days like today.
Recommended: Coway AP-1512HH Mighty — True HEPA + carbon · CADR ~246 CFM · rooms up to 361 sq ft
As an Amazon Associate, we earn from qualifying purchases.
How is the air in San Antonio in September?
Moderate on a typical day: median AQI 55 across 2019–2025, with 9.1% of September days above AQI 100. Ground-level ozone is the main driver.
- ✓32.9% of September days were Good (AQI 0–50), 58.1% Moderate (51–100).
- ✓19 days of 210 reached AQI 101+; the September peak was 154.
- ✓Best September: 2019; worst September: 2021.
Frequently asked questions
What is the air quality like in San Antonio in September?▾
Across 2019–2025, the median daily AQI in San Antonio in September was 55 (Moderate). 32.9% of days were Good, 58.1% Moderate, and 9.1% reached Unhealthy for Sensitive Groups or worse, based on 210 monitored days in EPA's Air Quality System.
Is September a good time for outdoor exercise in San Antonio?▾
A typical September day in San Antonio is Moderate (median AQI 55): outdoor exercise is acceptable for most people, but unusually sensitive individuals should watch for symptoms, and about 1 day in 11 of September days (9.1%) reached AQI 101+ — the level at which EPA advises people with asthma, children and older adults to shorten hard outdoor exertion.
Which pollutant causes San Antonio's September air quality problems?▾
Ground-level ozone set the daily AQI on 57.6% of September days in San Antonio. The highest September AQI recorded in 2019–2025 was 154 (Unhealthy), in 2021.
San Antonio September air quality, year by year
San Antonio September air quality by year (San Antonio-New Braunfels, TX, EPA AQS daily AQI)
| Year | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| 2019cleanest | 30 | 52 | 0 | 74 | PM2.5 |
| 2020 | 30 | 55 | 0 | 80 | PM2.5 |
| 2021worst | 30 | 71 | 5 | 147 | PM2.5 |
| 2022 | 30 | 68 | 5 | 129 | O3 |
| 2023 | 30 | 54 | 5 | 136 | O3 |
| 2024 | 30 | 49 | 1 | 119 | O3 |
| 2025 | 30 | 60 | 3 | 154 | O3 |
What September air means in San Antonio
A typical September day in San Antonio is Moderate (median AQI 55): outdoor exercise is acceptable for most people, but unusually sensitive individuals should watch for symptoms, and about 1 day in 11 of September days (9.1%) reached AQI 101+ — the level at which EPA advises people with asthma, children and older adults to shorten hard outdoor exertion.
September's median AQI of 55 is in line with San Antonio's whole-year median of 55, so this period is neither a clean nor a dirty stretch for the area. Nationally, the median September AQI across every EPA metro area (100,699 metro-days, 2019–2025) is 43, so San Antonio runs above the national September norm; 9.1% of its September days topped AQI 100 versus 2.7% nationally (above average).
September is part of San Antonio's fall season (September, October, November); the fall page pools all three months.
Activity-specific thresholds: running, cycling, kids' sports.
Right now in San Antonio
The latest EPA AirNow observation puts San Antonio's AQI at 52 (PM2.5). The figures above are multi-year month statistics, not today's reading.
View current San Antonio air quality →Source: EPA Air Quality System (AQS) pre-generated Daily AQI by CBSA files — daily AQI by CBSA (San Antonio-New Braunfels, TX), 2019–2025. Daily AQI per CBSA is the highest AQI reported by any monitor in the area that day; the defining parameter is the pollutant that set it. Month and season statistics pool every such day in the period across all years listed. Retrieved 2026-09-09.