Louisville Air Quality in 2019
In 2019, Louisville's air quality (Louisville/Jefferson County, KY-IN area) had a median daily AQI of 55 (Moderate) across 365 monitored days. 4 days (1.1%) reached Unhealthy for Sensitive Groups or worse, 121 were Good, and the year's peak AQI was 136 (Unhealthy for Sensitive Groups). Fine particulate matter (PM2.5) set the daily AQI on 263 of those days. The cleanest month of 2019 was October (median AQI 51, 0 days above 100) and the worst was July (median 57, 2 days above 100, peak 122).
- Good: 33.2%
- Moderate: 65.8%
- Unhealthy for Sensitive Groups: 1.1%
- Unhealthy or worse: 0.0%
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How was Louisville's air quality in 2019?
Moderate on a typical day: median AQI 55, with 4 days above AQI 100 out of 365 monitored — the 1st cleanest of 7 years on record for the area.
- ✓Peak AQI in 2019: 136 (Unhealthy for Sensitive Groups).
- ✓Fine particulate matter (PM2.5) was the main pollutant on 263 days.
- ✓Cleanest month: October; worst: July.
Frequently asked questions
What was the average AQI in Louisville in 2019?▾
EPA's Air Quality System puts Louisville's (Louisville/Jefferson County, KY-IN) median daily AQI for 2019 at 55, which is Moderate. 4 days were Unhealthy for Sensitive Groups or worse and the year's highest AQI was 136.
Which month had the worst air quality in Louisville in 2019?▾
The cleanest month of 2019 was October (median AQI 51, 0 days above 100) and the worst was July (median 57, 2 days above 100, peak 122).
Was 2019 a good or bad year for Louisville's air?▾
Among the 7 years EPA has published for the area (2019–2025), 2019 ranks 1st cleanest by days above AQI 100 — the best year on record here. 2019's median of 55 is in line with the area's typical annual median of 54.
Louisville month by month in 2019
Louisville air quality month by month, 2019 (Louisville/Jefferson County, KY-IN, EPA AQS daily AQI)
| Month | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| January | 31 | 57 | 0 | 71 | PM2.5 |
| February | 28 | 58 | 0 | 74 | PM2.5 |
| March | 31 | 55 | 0 | 78 | PM2.5 |
| April | 30 | 52 | 0 | 67 | O3 |
| May | 31 | 55 | 0 | 93 | PM2.5 |
| June | 30 | 50 | 1 | 101 | PM2.5 |
| Julyworst | 31 | 57 | 2 | 122 | PM2.5 |
| August | 31 | 54 | 1 | 136 | O3 |
| September | 30 | 61 | 0 | 97 | O3 |
| Octobercleanest | 31 | 51 | 0 | 67 | PM2.5 |
| November | 30 | 54 | 0 | 86 | PM2.5 |
| December | 31 | 60 | 0 | 93 | PM2.5 |
How 2019 compares
Among the 7 years EPA has published for the area (2019–2025), 2019 ranks 1st cleanest by days above AQI 100 — the best year on record here.
2019's median of 55 is in line with the area's typical annual median of 54.
Activity-specific thresholds: running, cycling, kids' sports.
Right now in Louisville
The latest EPA AirNow observation puts Louisville's AQI at 36 (PM2.5). The figures above are multi-year annual 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.