Louisville Air Quality in December
Across 2019–2025, Louisville's December air quality had a median AQI of 54 (Moderate) over 217 monitored days in the Louisville/Jefferson County, KY-IN area. 0.0% of December days (0 of 217) reached Unhealthy for Sensitive Groups or worse, and fine particulate matter (PM2.5) set the daily AQI on 94.9% of days. The cleanest December on record here was 2024 (median AQI 43, 0 days above 100) and the worst was 2020 (median 60, 0 days above 100, peak AQI 78).
- Good: 36.4%
- Moderate: 63.6%
- Unhealthy for Sensitive Groups: 0.0%
- Unhealthy or worse: 0.0%
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How is the air in Louisville in December?
Moderate on a typical day: median AQI 54 across 2019–2025, with 0.0% of December days above AQI 100. Fine particulate matter (PM2.5) is the main driver.
- ✓36.4% of December days were Good (AQI 0–50), 63.6% Moderate (51–100).
- ✓0 days of 217 reached AQI 101+; the December peak was 93.
- ✓Best December: 2024; worst December: 2020.
Frequently asked questions
What is the air quality like in Louisville in December?▾
Across 2019–2025, the median daily AQI in Louisville in December was 54 (Moderate). 36.4% of days were Good, 63.6% Moderate, and 0.0% reached Unhealthy for Sensitive Groups or worse, based on 217 monitored days in EPA's Air Quality System.
Is December a good time for outdoor exercise in Louisville?▾
A typical December day in Louisville is Moderate (median AQI 54): outdoor exercise is acceptable for most people, but unusually sensitive individuals should watch for symptoms, and fewer than 1% of December days reached AQI 101+ — the level at which EPA advises people with asthma, children and older adults to shorten hard outdoor exertion.
Which pollutant causes Louisville's December air quality problems?▾
Fine particulate matter (PM2.5) set the daily AQI on 94.9% of December days in Louisville. The highest December AQI recorded in 2019–2025 was 93 (Moderate), in 2020.
Louisville December air quality, year by year
Louisville December air quality by year (Louisville/Jefferson County, KY-IN, EPA AQS daily AQI)
| Year | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| 2019 | 31 | 60 | 0 | 93 | PM2.5 |
| 2020worst | 31 | 60 | 0 | 78 | PM2.5 |
| 2021 | 31 | 56 | 0 | 72 | PM2.5 |
| 2022 | 31 | 54 | 0 | 69 | PM2.5 |
| 2023 | 31 | 52 | 0 | 70 | PM2.5 |
| 2024cleanest | 31 | 43 | 0 | 57 | PM2.5 |
| 2025 | 31 | 56 | 0 | 80 | PM2.5 |
What December air means in Louisville
A typical December day in Louisville is Moderate (median AQI 54): outdoor exercise is acceptable for most people, but unusually sensitive individuals should watch for symptoms, and fewer than 1% of December days reached AQI 101+ — the level at which EPA advises people with asthma, children and older adults to shorten hard outdoor exertion.
December's median AQI of 54 is in line with Louisville's whole-year median of 54, so this period is neither a clean nor a dirty stretch for the area. Nationally, the median December AQI across every EPA metro area (95,590 metro-days, 2019–2025) is 39, so Louisville runs above the national December norm; 0.0% of its December days topped AQI 100 versus 0.7% nationally (about the same).
December is part of Louisville's winter season (December, January, February); the winter page pools all three months.
Activity-specific thresholds: running, cycling, kids' sports.
Right now in Louisville
The latest EPA AirNow observation puts Louisville's AQI at 38 (PM2.5). The figures above are multi-year month statistics, not today's reading.
View current Louisville air quality →Source: EPA Air Quality System (AQS) pre-generated Daily AQI by CBSA files — daily AQI by CBSA (Louisville/Jefferson County, KY-IN), 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.