Knoxville Air Quality in September
Across 2019–2025, Knoxville's September air quality had a median AQI of 51 (Moderate) over 210 monitored days in the Knoxville, TN area. 1.0% of September days (2 of 210) reached Unhealthy for Sensitive Groups or worse, and fine particulate matter (PM2.5) set the daily AQI on 53.8% of days. The cleanest September on record here was 2020 (median AQI 44, 0 days above 100) and the worst was 2019 (median 61, 2 days above 100, peak AQI 105).
- Good: 47.6%
- Moderate: 51.4%
- Unhealthy for Sensitive Groups: 1.0%
- Unhealthy or worse: 0.0%
Extra Protection for Knoxville Homes
Air quality in Knoxville is moderate (AQI 61), 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 Knoxville in September?
Moderate on a typical day: median AQI 51 across 2019–2025, with 1.0% of September days above AQI 100. Fine particulate matter (PM2.5) is the main driver.
- ✓47.6% of September days were Good (AQI 0–50), 51.4% Moderate (51–100).
- ✓2 days of 210 reached AQI 101+; the September peak was 105.
- ✓Best September: 2020; worst September: 2019.
Frequently asked questions
What is the air quality like in Knoxville in September?▾
Across 2019–2025, the median daily AQI in Knoxville in September was 51 (Moderate). 47.6% of days were Good, 51.4% Moderate, and 1.0% 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 Knoxville?▾
A typical September day in Knoxville is Moderate (median AQI 51): outdoor exercise is acceptable for most people, but unusually sensitive individuals should watch for symptoms, and about 1 day in 100 of September days (1.0%) reached AQI 101+ — the level at which EPA advises people with asthma, children and older adults to shorten hard outdoor exertion.
Which pollutant causes Knoxville's September air quality problems?▾
Fine particulate matter (PM2.5) set the daily AQI on 53.8% of September days in Knoxville. The highest September AQI recorded in 2019–2025 was 105 (Unhealthy for Sensitive Groups), in 2019.
Knoxville September air quality, year by year
Knoxville September air quality by year (Knoxville, TN, EPA AQS daily AQI)
| Year | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| 2019worst | 30 | 61 | 2 | 105 | O3 |
| 2020cleanest | 30 | 44 | 0 | 72 | PM2.5 |
| 2021 | 30 | 53 | 0 | 73 | PM2.5 |
| 2022 | 30 | 44 | 0 | 67 | O3 |
| 2023 | 30 | 53 | 0 | 64 | PM2.5 |
| 2024 | 30 | 44 | 0 | 77 | O3 |
| 2025 | 30 | 53 | 0 | 80 | O3 |
What September air means in Knoxville
A typical September day in Knoxville is Moderate (median AQI 51): outdoor exercise is acceptable for most people, but unusually sensitive individuals should watch for symptoms, and about 1 day in 100 of September days (1.0%) 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 51 is in line with Knoxville'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 Knoxville runs above the national September norm; 1.0% of its September days topped AQI 100 versus 2.7% nationally (below average).
September is part of Knoxville's fall season (September, October, November); the fall page pools all three months.
Activity-specific thresholds: running, cycling, kids' sports.
Right now in Knoxville
The latest EPA AirNow observation puts Knoxville's AQI at 61 (PM2.5). The figures above are multi-year month statistics, not today's reading.
View current Knoxville air quality →Source: EPA Air Quality System (AQS) pre-generated Daily AQI by CBSA files — daily AQI by CBSA (Knoxville, TN), 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.