Louisville Air Quality in Winter
Across 2019–2025, Louisville's winter (December–February) air quality had a median AQI of 54 (Moderate) over 632 monitored days in the Louisville/Jefferson County, KY-IN area. 0.0% of winter days (0 of 632) reached Unhealthy for Sensitive Groups or worse, and fine particulate matter (PM2.5) set the daily AQI on 93.8% of days. The cleanest winter on record here was 2024 (median AQI 47, 0 days above 100) and the worst was 2019 (median 58, 0 days above 100, peak AQI 93).
- Good: 35.9%
- Moderate: 64.1%
- Unhealthy for Sensitive Groups: 0.0%
- Unhealthy or worse: 0.0%
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How is the air in Louisville in winter?
Moderate on a typical day: median AQI 54 across 2019–2025, with 0.0% of winter days above AQI 100. Fine particulate matter (PM2.5) is the main driver.
- ✓35.9% of winter days were Good (AQI 0–50), 64.1% Moderate (51–100).
- ✓0 days of 632 reached AQI 101+; the winter peak was 93.
- ✓Cleanest month: December; worst month: February.
Frequently asked questions
What is the air quality like in Louisville in winter?▾
Across 2019–2025, the median daily AQI in Louisville in winter was 54 (Moderate). 35.9% of days were Good, 64.1% Moderate, and 0.0% reached Unhealthy for Sensitive Groups or worse, based on 632 monitored days in EPA's Air Quality System.
Is winter a good time for outdoor exercise in Louisville?▾
A typical winter 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 winter 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 winter air quality problems?▾
Fine particulate matter (PM2.5) set the daily AQI on 93.8% of winter days in Louisville. The highest winter AQI recorded in 2019–2025 was 93 (Moderate), in 2019.
Louisville winter air quality, year by year
Louisville winter 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 |
|---|---|---|---|---|---|
| 2019worst | 90 | 58 | 0 | 93 | PM2.5 |
| 2020 | 91 | 55 | 0 | 78 | PM2.5 |
| 2021 | 90 | 56 | 0 | 91 | PM2.5 |
| 2022 | 90 | 55 | 0 | 91 | PM2.5 |
| 2023 | 90 | 54 | 0 | 72 | PM2.5 |
| 2024cleanest | 91 | 47 | 0 | 74 | PM2.5 |
| 2025 | 90 | 54 | 0 | 82 | PM2.5 |
What winter air means in Louisville
A typical winter 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 winter days reached AQI 101+ — the level at which EPA advises people with asthma, children and older adults to shorten hard outdoor exertion.
Winter'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 Winter AQI across every EPA metro area (278,620 metro-days, 2019–2025) is 40, so Louisville runs above the national Winter norm; 0.0% of its Winter days topped AQI 100 versus 0.6% nationally (about the same).
Within the season, December is the cleanest month (median AQI 54, 0.0% of days above 100) and February the worst (median 55, 0.0% above 100).
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 season 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.