Knoxville Air Quality in Fall
Across 2019–2025, Knoxville's fall (September–November) air quality had a median AQI of 50 (Good) over 637 monitored days in the Knoxville, TN area. 0.5% of fall days (3 of 637) reached Unhealthy for Sensitive Groups or worse, and fine particulate matter (PM2.5) set the daily AQI on 66.2% of days. The cleanest fall on record here was 2025 (median AQI 44, 0 days above 100) and the worst was 2019 (median 53, 2 days above 100, peak AQI 105).
- Good: 50.1%
- Moderate: 49.5%
- Unhealthy for Sensitive Groups: 0.3%
- Unhealthy or worse: 0.2%
Reduce Indoor Ozone in Knoxville
Today's main pollutant in Knoxville is ground-level ozone (AQI 29). 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 Knoxville in fall?
Good on a typical day: median AQI 50 across 2019–2025, with 0.5% of fall days above AQI 100. Fine particulate matter (PM2.5) is the main driver.
- ✓50.1% of fall days were Good (AQI 0–50), 49.5% Moderate (51–100).
- ✓3 days of 637 reached AQI 101+; the fall peak was 162.
- ✓Cleanest month: November; worst month: September.
Frequently asked questions
What is the air quality like in Knoxville in fall?▾
Across 2019–2025, the median daily AQI in Knoxville in fall was 50 (Good). 50.1% of days were Good, 49.5% Moderate, and 0.5% reached Unhealthy for Sensitive Groups or worse, based on 637 monitored days in EPA's Air Quality System.
Is fall a good time for outdoor exercise in Knoxville?▾
A typical fall day in Knoxville sits in the Good range (median AQI 50), so running, cycling and children's outdoor play are fine for everyone on most days; fewer than 1% of fall days reached AQI 101+ in 2019–2025.
Which pollutant causes Knoxville's fall air quality problems?▾
Fine particulate matter (PM2.5) set the daily AQI on 66.2% of fall days in Knoxville. The highest fall AQI recorded in 2019–2025 was 162 (Unhealthy), in 2019.
Knoxville fall air quality, year by year
Knoxville fall air quality by year (Knoxville, TN, EPA AQS daily AQI)
| Year | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| 2019worst | 91 | 53 | 2 | 105 | PM2.5 |
| 2020 | 91 | 49 | 0 | 77 | PM2.5 |
| 2021 | 91 | 52 | 0 | 73 | PM2.5 |
| 2022 | 91 | 48 | 1 | 162 | PM2.5 |
| 2023 | 91 | 51 | 0 | 78 | PM2.5 |
| 2024 | 91 | 49 | 0 | 77 | PM2.5 |
| 2025cleanest | 91 | 44 | 0 | 80 | O3 |
What fall air means in Knoxville
A typical fall day in Knoxville sits in the Good range (median AQI 50), so running, cycling and children's outdoor play are fine for everyone on most days; fewer than 1% of fall days reached AQI 101+ in 2019–2025.
Fall's median AQI of 50 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 Fall AQI across every EPA metro area (296,275 metro-days, 2019–2025) is 40, so Knoxville runs above the national Fall norm; 0.5% of its Fall days topped AQI 100 versus 1.5% nationally (about the same).
Within the season, November is the cleanest month (median AQI 52, 0.0% of days above 100) and September the worst (median 51, 1.0% above 100).
Activity-specific thresholds: running, cycling, kids' sports.
Right now in Knoxville
The latest EPA AirNow observation puts Knoxville's AQI at 29 (O3). The figures above are multi-year season 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.