Houston Air Quality in September
Across 2019–2025, Houston's September air quality had a median AQI of 74 (Moderate) over 210 monitored days in the Houston-The Woodlands-Sugar Land, TX area. 28.1% of September days (59 of 210) reached Unhealthy for Sensitive Groups or worse, and ground-level ozone set the daily AQI on 61.0% of days. The cleanest September on record here was 2020 (median AQI 55, 0 days above 100) and the worst was 2023 (median 86, 14 days above 100, peak AQI 179).
- Good: 16.2%
- Moderate: 55.7%
- Unhealthy for Sensitive Groups: 21.0%
- Unhealthy or worse: 7.1%
Extra Protection for Houston Homes
Air quality in Houston is moderate (AQI 57), 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
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How is the air in Houston in September?
Moderate on a typical day: median AQI 74 across 2019–2025, with 28.1% of September days above AQI 100. Ground-level ozone is the main driver.
- ✓16.2% of September days were Good (AQI 0–50), 55.7% Moderate (51–100).
- ✓59 days of 210 reached AQI 101+; the September peak was 179.
- ✓Best September: 2020; worst September: 2023.
Frequently asked questions
What is the air quality like in Houston in September?▾
Across 2019–2025, the median daily AQI in Houston in September was 74 (Moderate). 16.2% of days were Good, 55.7% Moderate, and 28.1% 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 Houston?▾
A typical September day in Houston is Moderate (median AQI 74): outdoor exercise is acceptable for most people, but unusually sensitive individuals should watch for symptoms, and about 1 day in 4 of September days (28.1%) reached AQI 101+ — the level at which EPA advises people with asthma, children and older adults to shorten hard outdoor exertion.
Which pollutant causes Houston's September air quality problems?▾
Ground-level ozone set the daily AQI on 61.0% of September days in Houston. The highest September AQI recorded in 2019–2025 was 179 (Unhealthy), in 2023.
Houston September air quality, year by year
Houston September air quality by year (Houston-The Woodlands-Sugar Land, TX, EPA AQS daily AQI)
| Year | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| 2019 | 30 | 55 | 3 | 169 | O3 |
| 2020cleanest | 30 | 55 | 0 | 90 | PM2.5 |
| 2021 | 30 | 82 | 11 | 159 | O3 |
| 2022 | 30 | 91 | 10 | 166 | O3 |
| 2023worst | 30 | 86 | 14 | 179 | O3 |
| 2024 | 30 | 73 | 8 | 159 | O3 |
| 2025 | 30 | 100 | 13 | 154 | O3 |
What September air means in Houston
A typical September day in Houston is Moderate (median AQI 74): outdoor exercise is acceptable for most people, but unusually sensitive individuals should watch for symptoms, and about 1 day in 4 of September days (28.1%) 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 74 is above Houston's whole-year median of 61, making it one of the area's dirtier periods. Nationally, the median September AQI across every EPA metro area (100,699 metro-days, 2019–2025) is 43, so Houston runs above the national September norm; 28.1% of its September days topped AQI 100 versus 2.7% nationally (above average).
September is part of Houston's fall season (September, October, November); the fall page pools all three months.
Activity-specific thresholds: running, cycling, kids' sports.
Right now in Houston
The latest EPA AirNow observation puts Houston's AQI at 57 (PM2.5). The figures above are multi-year month statistics, not today's reading.
View current Houston air quality →Source: EPA Air Quality System (AQS) pre-generated Daily AQI by CBSA files — daily AQI by CBSA (Houston-The Woodlands-Sugar Land, 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.