Brownsville Air Quality in September
Across 2019–2025, Brownsville's September air quality had a median AQI of 45 (Good) over 210 monitored days in the Brownsville-Harlingen, TX area. 1.5% of September days (3 of 210) reached Unhealthy for Sensitive Groups or worse, and fine particulate matter (PM2.5) set the daily AQI on 71.0% of days. The cleanest September on record here was 2023 (median AQI 33, 0 days above 100) and the worst was 2024 (median 45, 2 days above 100, peak AQI 152).
- Good: 60.5%
- Moderate: 38.1%
- Unhealthy for Sensitive Groups: 1.0%
- Unhealthy or worse: 0.5%
Improve Indoor Air Quality
Even with good outdoor air in Brownsville, indoor PM2.5, dust and allergens build up. A True-HEPA purifier keeps a bedroom or office consistently clean.
Recommended: Levoit Core 400S — True HEPA · CADR ~141 CFM · rooms up to 219 sq ft
As an Amazon Associate, we earn from qualifying purchases.
How is the air in Brownsville in September?
Good on a typical day: median AQI 45 across 2019–2025, with 1.5% of September days above AQI 100. Fine particulate matter (PM2.5) is the main driver.
- ✓60.5% of September days were Good (AQI 0–50), 38.1% Moderate (51–100).
- ✓3 days of 210 reached AQI 101+; the September peak was 152.
- ✓Best September: 2023; worst September: 2024.
Frequently asked questions
What is the air quality like in Brownsville in September?▾
Across 2019–2025, the median daily AQI in Brownsville in September was 45 (Good). 60.5% of days were Good, 38.1% Moderate, and 1.5% 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 Brownsville?▾
A typical September day in Brownsville sits in the Good range (median AQI 45), so running, cycling and children's outdoor play are fine for everyone on most days; about 1 day in 67 of September days (1.5%) reached AQI 101+ in 2019–2025.
Which pollutant causes Brownsville's September air quality problems?▾
Fine particulate matter (PM2.5) set the daily AQI on 71.0% of September days in Brownsville. The highest September AQI recorded in 2019–2025 was 152 (Unhealthy), in 2024.
Brownsville September air quality, year by year
Brownsville September air quality by year (Brownsville-Harlingen, TX, EPA AQS daily AQI)
| Year | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| 2019 | 30 | 39 | 0 | 53 | PM2.5 |
| 2020 | 30 | 55 | 1 | 101 | PM2.5 |
| 2021 | 30 | 49 | 0 | 89 | PM2.5 |
| 2022 | 30 | 39 | 0 | 61 | O3 |
| 2023cleanest | 30 | 33 | 0 | 62 | O3 |
| 2024worst | 30 | 45 | 2 | 152 | PM2.5 |
| 2025 | 30 | 61 | 0 | 84 | PM2.5 |
What September air means in Brownsville
A typical September day in Brownsville sits in the Good range (median AQI 45), so running, cycling and children's outdoor play are fine for everyone on most days; about 1 day in 67 of September days (1.5%) reached AQI 101+ in 2019–2025.
September's median AQI of 45 is below Brownsville's whole-year median of 52, making it one of the area's cleaner periods. Nationally, the median September AQI across every EPA metro area (100,699 metro-days, 2019–2025) is 43, so Brownsville runs in line with the national September norm; 1.5% of its September days topped AQI 100 versus 2.7% nationally (below average).
September is part of Brownsville's fall season (September, October, November); the fall page pools all three months.
Activity-specific thresholds: running, cycling, kids' sports.
Right now in Brownsville
The latest EPA AirNow observation puts Brownsville's AQI at 47 (PM2.5). The figures above are multi-year month statistics, not today's reading.
View current Brownsville air quality →Source: EPA Air Quality System (AQS) pre-generated Daily AQI by CBSA files — daily AQI by CBSA (Brownsville-Harlingen, 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.