Durham Air Quality in September
Across 2019–2025, Durham's September air quality had a median AQI of 42 (Good) over 210 monitored days in the Durham-Chapel Hill, NC area. 0.0% of September days (0 of 210) reached Unhealthy for Sensitive Groups or worse, and ground-level ozone set the daily AQI on 59.0% of days. The cleanest September on record here was 2020 (median AQI 34, 0 days above 100) and the worst was 2019 (median 49, 0 days above 100, peak AQI 74).
- Good: 74.3%
- Moderate: 25.7%
- Unhealthy for Sensitive Groups: 0.0%
- Unhealthy or worse: 0.0%
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How is the air in Durham in September?
Good on a typical day: median AQI 42 across 2019–2025, with 0.0% of September days above AQI 100. Ground-level ozone is the main driver.
- ✓74.3% of September days were Good (AQI 0–50), 25.7% Moderate (51–100).
- ✓0 days of 210 reached AQI 101+; the September peak was 74.
- ✓Best September: 2020; worst September: 2019.
Frequently asked questions
What is the air quality like in Durham in September?▾
Across 2019–2025, the median daily AQI in Durham in September was 42 (Good). 74.3% of days were Good, 25.7% Moderate, and 0.0% 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 Durham?▾
A typical September day in Durham sits in the Good range (median AQI 42), so running, cycling and children's outdoor play are fine for everyone on most days; fewer than 1% of September days reached AQI 101+ in 2019–2025.
Which pollutant causes Durham's September air quality problems?▾
Ground-level ozone set the daily AQI on 59.0% of September days in Durham. The highest September AQI recorded in 2019–2025 was 74 (Moderate), in 2019.
Durham September air quality, year by year
Durham September air quality by year (Durham-Chapel Hill, NC, EPA AQS daily AQI)
| Year | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| 2019worst | 30 | 49 | 0 | 74 | O3 |
| 2020cleanest | 30 | 34 | 0 | 63 | O3 |
| 2021 | 30 | 44 | 0 | 61 | O3 |
| 2022 | 30 | 40 | 0 | 56 | O3 |
| 2023 | 30 | 41 | 0 | 67 | O3 |
| 2024 | 30 | 43 | 0 | 57 | PM2.5 |
| 2025 | 30 | 43 | 0 | 67 | O3 |
What September air means in Durham
A typical September day in Durham sits in the Good range (median AQI 42), so running, cycling and children's outdoor play are fine for everyone on most days; fewer than 1% of September days reached AQI 101+ in 2019–2025.
September's median AQI of 42 is in line with Durham's whole-year median of 44, 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 Durham runs in line with the national September norm; 0.0% of its September days topped AQI 100 versus 2.7% nationally (below average).
September is part of Durham's fall season (September, October, November); the fall page pools all three months.
Activity-specific thresholds: running, cycling, kids' sports.
Right now in Durham
The latest EPA AirNow observation puts Durham's AQI at 41 (PM2.5). The figures above are multi-year month statistics, not today's reading.
View current Durham air quality →Source: EPA Air Quality System (AQS) pre-generated Daily AQI by CBSA files — daily AQI by CBSA (Durham-Chapel Hill, NC), 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.