Louisville Air Quality in 2021
In 2021, Louisville's air quality (Louisville/Jefferson County, KY-IN area) had a median daily AQI of 54 (Moderate) across 365 monitored days. 7 days (1.9%) reached Unhealthy for Sensitive Groups or worse, 133 were Good, and the year's peak AQI was 143 (Unhealthy for Sensitive Groups). Fine particulate matter (PM2.5) set the daily AQI on 293 of those days. The cleanest month of 2021 was October (median AQI 51, 0 days above 100) and the worst was July (median 65, 3 days above 100, peak 143).
- Good: 36.4%
- Moderate: 61.6%
- Unhealthy for Sensitive Groups: 1.9%
- Unhealthy or worse: 0.0%
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How was Louisville's air quality in 2021?
Moderate on a typical day: median AQI 54, with 7 days above AQI 100 out of 365 monitored — the 3rd cleanest of 7 years on record for the area.
- ✓Peak AQI in 2021: 143 (Unhealthy for Sensitive Groups).
- ✓Fine particulate matter (PM2.5) was the main pollutant on 293 days.
- ✓Cleanest month: October; worst: July.
Frequently asked questions
What was the average AQI in Louisville in 2021?▾
EPA's Air Quality System puts Louisville's (Louisville/Jefferson County, KY-IN) median daily AQI for 2021 at 54, which is Moderate. 7 days were Unhealthy for Sensitive Groups or worse and the year's highest AQI was 143.
Which month had the worst air quality in Louisville in 2021?▾
The cleanest month of 2021 was October (median AQI 51, 0 days above 100) and the worst was July (median 65, 3 days above 100, peak 143).
Was 2021 a good or bad year for Louisville's air?▾
Among the 7 years EPA has published for the area (2019–2025), 2021 ranks 3rd cleanest by days above AQI 100. 2021's median of 54 is in line with the area's typical annual median of 54.
Louisville month by month in 2021
Louisville air quality month by month, 2021 (Louisville/Jefferson County, KY-IN, EPA AQS daily AQI)
| Month | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| January | 31 | 54 | 0 | 80 | PM2.5 |
| February | 28 | 58 | 0 | 91 | PM2.5 |
| March | 31 | 55 | 0 | 79 | PM2.5 |
| April | 30 | 54 | 0 | 74 | PM2.5 |
| May | 31 | 51 | 1 | 108 | O3 |
| June | 30 | 53 | 1 | 126 | PM2.5 |
| Julyworst | 31 | 65 | 3 | 143 | PM2.5 |
| August | 31 | 58 | 1 | 105 | PM2.5 |
| September | 30 | 48 | 1 | 112 | PM2.5 |
| Octobercleanest | 31 | 51 | 0 | 63 | PM2.5 |
| November | 30 | 53 | 0 | 96 | PM2.5 |
| December | 31 | 56 | 0 | 72 | PM2.5 |
How 2021 compares
Among the 7 years EPA has published for the area (2019–2025), 2021 ranks 3rd cleanest by days above AQI 100.
2021's median of 54 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.