Austin Air Quality in September
Across 2019–2025, Austin's September air quality had a median AQI of 52 (Moderate) over 210 monitored days in the Austin-Round Rock, TX area. 4.3% of September days (9 of 210) reached Unhealthy for Sensitive Groups or worse, and ground-level ozone set the daily AQI on 55.7% of days. The cleanest September on record here was 2024 (median AQI 48, 0 days above 100) and the worst was 2023 (median 54, 5 days above 100, peak AQI 119).
- Good: 43.3%
- Moderate: 52.4%
- Unhealthy for Sensitive Groups: 4.3%
- Unhealthy or worse: 0.0%
Reduce Indoor Ozone in Austin
Today's main pollutant in Austin is ground-level ozone (AQI 33). Important: standard HEPA filters do NOT remove ozone — only a purifier with a substantial activated-carbon bed adsorbs it. The biggest wins are cutting indoor sources (gas appliances, certain "ionizer" purifiers) and ventilating when outdoor ozone is low (early morning). A high-carbon unit helps with the gases and VOCs that linger indoors.
Recommended: Levoit Core 300 — True HEPA + activated carbon · CADR ~141 CFM · rooms up to 219 sq ft
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How is the air in Austin in September?
Moderate on a typical day: median AQI 52 across 2019–2025, with 4.3% of September days above AQI 100. Ground-level ozone is the main driver.
- ✓43.3% of September days were Good (AQI 0–50), 52.4% Moderate (51–100).
- ✓9 days of 210 reached AQI 101+; the September peak was 129.
- ✓Best September: 2024; worst September: 2023.
Frequently asked questions
What is the air quality like in Austin in September?▾
Across 2019–2025, the median daily AQI in Austin in September was 52 (Moderate). 43.3% of days were Good, 52.4% Moderate, and 4.3% 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 Austin?▾
A typical September day in Austin is Moderate (median AQI 52): outdoor exercise is acceptable for most people, but unusually sensitive individuals should watch for symptoms, and about 1 day in 23 of September days (4.3%) reached AQI 101+ — the level at which EPA advises people with asthma, children and older adults to shorten hard outdoor exertion.
Which pollutant causes Austin's September air quality problems?▾
Ground-level ozone set the daily AQI on 55.7% of September days in Austin. The highest September AQI recorded in 2019–2025 was 129 (Unhealthy for Sensitive Groups), in 2023.
Austin September air quality, year by year
Austin September air quality by year (Austin-Round Rock, TX, EPA AQS daily AQI)
| Year | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| 2019 | 30 | 48 | 1 | 112 | PM2.5 |
| 2020 | 30 | 52 | 0 | 77 | PM2.5 |
| 2021 | 30 | 61 | 0 | 90 | O3 |
| 2022 | 30 | 60 | 2 | 129 | O3 |
| 2023worst | 30 | 54 | 5 | 119 | O3 |
| 2024cleanest | 30 | 48 | 0 | 84 | O3 |
| 2025 | 30 | 61 | 1 | 129 | O3 |
What September air means in Austin
A typical September day in Austin is Moderate (median AQI 52): outdoor exercise is acceptable for most people, but unusually sensitive individuals should watch for symptoms, and about 1 day in 23 of September days (4.3%) 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 52 is in line with Austin's whole-year median of 52, 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 Austin runs above the national September norm; 4.3% of its September days topped AQI 100 versus 2.7% nationally (above average).
September is part of Austin's fall season (September, October, November); the fall page pools all three months.
Activity-specific thresholds: running, cycling, kids' sports.
Right now in Austin
The latest EPA AirNow observation puts Austin's AQI at 33 (O3). The figures above are multi-year month statistics, not today's reading.
View current Austin air quality →Source: EPA Air Quality System (AQS) pre-generated Daily AQI by CBSA files — daily AQI by CBSA (Austin-Round Rock, 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.