Louisville Best & Worst AQI Days: Air Quality Guide
The worst air quality day on record for Louisville (Louisville/Jefferson County, KY-IN area) was June 28, 2023, when the daily AQI reached 182 (Unhealthy), set by fine particulate matter (PM2.5), in wildfire smoke season. Across 2,557 monitored days in 2019–2025, 3 of the 10 worst days were Unhealthy (AQI 151+) or worse; 8 of the 10 were driven by ground-level ozone and 2 by fine particulate matter (PM2.5), and 4 of them fell in 2024. The cleanest day was January 26, 2024 at AQI 19 (Good); the 10 best days span 6 different years.
Extra Protection for Louisville Homes
Air quality in Louisville is moderate (AQI 61), with fine particles (PM2.5) the main concern. A True-HEPA purifier gives sensitive groups — kids, seniors and anyone with asthma or allergies — cleaner air indoors on days like today.
Recommended: Coway AP-1512HH Mighty — True HEPA + carbon · CADR ~246 CFM · rooms up to 361 sq ft
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When were Louisville's worst and best air quality days?
Worst: June 28, 2023, AQI 182 (Unhealthy, PM2.5). Best: January 26, 2024, AQI 19 (Good). Based on 2,557 EPA-monitored days in the Louisville/Jefferson County, KY-IN area, 2019–2025.
- ✓3 of the 10 worst days were Unhealthy (AQI 151+) or worse; the 10th-worst was AQI 140 (Unhealthy for Sensitive Groups).
- ✓Ground-level ozone drove 8 of the 10 worst days.
- ✓2024 accounts for 4 of the 10 worst days.
Frequently asked questions
What was the worst air quality day in Louisville?▾
June 28, 2023: the Louisville/Jefferson County, KY-IN area's daily AQI hit 182 (Unhealthy), driven by fine particulate matter (PM2.5), in wildfire smoke season. That is the highest of 2,557 monitored days in 2019–2025.
What was the best air quality day in Louisville?▾
January 26, 2024, with a daily AQI of 19 (Good). The daily AQI is the highest reading from any monitor in the area, so even the cleanest day reflects the area's worst monitor.
What was Louisville's worst air quality day in 2025?▾
July 5, 2025, AQI 153 (Unhealthy), set by fine particulate matter (PM2.5), in wildfire smoke season.
Which pollutant causes Louisville's worst air days?▾
Ground-level ozone set the AQI on 8 of the 10 worst days; fine particulate matter (PM2.5) on 2. The tables above list the defining pollutant for every day.
Louisville's 10 worst air quality days, 2019–2025
Highest daily AQI recorded for the Louisville/Jefferson County, KY-IN area (EPA AQS). The daily AQI is the highest reading from any monitor in the area that day.
| # | Date | AQI | Category | Defining pollutant |
|---|---|---|---|---|
| 1 | (2023 page) | 182 | Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
| 2 | (2024 page) | 156 | Unhealthy | O3 — ground-level ozone, in peak ozone season |
| 3 | (2025 page) | 153 | Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
| 4 | (2024 page) | 150 | Unhealthy for Sensitive Groups | O3 — ground-level ozone, in peak ozone season |
| 5 | (2023 page) | 150 | Unhealthy for Sensitive Groups | O3 — ground-level ozone, in peak ozone season |
| 6 | (2024 page) | 143 | Unhealthy for Sensitive Groups | O3 — ground-level ozone, in peak ozone season |
| 7 | (2021 page) | 143 | Unhealthy for Sensitive Groups | O3 — ground-level ozone, in peak ozone season |
| 8 | (2020 page) | 143 | Unhealthy for Sensitive Groups | O3 — ground-level ozone, in peak ozone season |
| 9 | (2025 page) | 140 | Unhealthy for Sensitive Groups | O3 — ground-level ozone |
| 10 | (2024 page) | 140 | Unhealthy for Sensitive Groups | O3 — ground-level ozone, in peak ozone season |
Worst day of each year in Louisville
The single highest-AQI day in each year on record. Click a year for its full month-by-month statistics.
| Year | Worst day | AQI | Category | Defining pollutant |
|---|---|---|---|---|
| 2019 | 136 | Unhealthy for Sensitive Groups | O3 — ground-level ozone, in peak ozone season | |
| 2020 | 143 | Unhealthy for Sensitive Groups | O3 — ground-level ozone, in peak ozone season | |
| 2021 | 143 | Unhealthy for Sensitive Groups | O3 — ground-level ozone, in peak ozone season | |
| 2022 | 136 | Unhealthy for Sensitive Groups | O3 — ground-level ozone, in peak ozone season | |
| 2023 | 182 | Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season | |
| 2024 | 156 | Unhealthy | O3 — ground-level ozone, in peak ozone season | |
| 2025 | 153 | Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
Louisville's 10 best air quality days, 2019–2025
Lowest daily AQI recorded for the Louisville/Jefferson County, KY-IN area. Ties are listed most recent first.
| # | Date | AQI | Category | Defining pollutant |
|---|---|---|---|---|
| 1 | (2024 page) | 19 | Good | O3 — ground-level ozone |
| 2 | (2021 page) | 20 | Good | O3 — ground-level ozone |
| 3 | (2025 page) | 21 | Good | O3 — ground-level ozone |
| 4 | (2023 page) | 21 | Good | PM2.5 — fine particulate matter (PM2.5) |
| 5 | (2024 page) | 22 | Good | O3 — ground-level ozone |
| 6 | (2022 page) | 22 | Good | O3 — ground-level ozone |
| 7 | (2020 page) | 22 | Good | O3 — ground-level ozone |
| 8 | (2025 page) | 23 | Good | O3 — ground-level ozone |
| 9 | (2025 page) | 23 | Good | PM2.5 — fine particulate matter (PM2.5) |
| 10 | (2024 page) | 23 | Good | PM2.5 — fine particulate matter (PM2.5) |
Right now in Louisville
The latest EPA AirNow observation puts Louisville's AQI at 61 (PM2.5). The days above are historical records, 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.