Louisville Air Quality in May
Across 2019–2025, Louisville's May air quality had a median AQI of 51 (Moderate) over 217 monitored days in the Louisville/Jefferson County, KY-IN area. 0.9% of May days (2 of 217) reached Unhealthy for Sensitive Groups or worse, and fine particulate matter (PM2.5) set the daily AQI on 52.5% of days. The cleanest May on record here was 2025 (median AQI 43, 0 days above 100) and the worst was 2023 (median 55, 1 day above 100, peak AQI 101).
- Good: 48.4%
- Moderate: 50.7%
- Unhealthy for Sensitive Groups: 0.9%
- Unhealthy or worse: 0.0%
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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How is the air in Louisville in May?
Moderate on a typical day: median AQI 51 across 2019–2025, with 0.9% of May days above AQI 100. Fine particulate matter (PM2.5) is the main driver.
- ✓48.4% of May days were Good (AQI 0–50), 50.7% Moderate (51–100).
- ✓2 days of 217 reached AQI 101+; the May peak was 108.
- ✓Best May: 2025; worst May: 2023.
Frequently asked questions
What is the air quality like in Louisville in May?▾
Across 2019–2025, the median daily AQI in Louisville in May was 51 (Moderate). 48.4% of days were Good, 50.7% Moderate, and 0.9% reached Unhealthy for Sensitive Groups or worse, based on 217 monitored days in EPA's Air Quality System.
Is May a good time for outdoor exercise in Louisville?▾
A typical May day in Louisville is Moderate (median AQI 51): outdoor exercise is acceptable for most people, but unusually sensitive individuals should watch for symptoms, and fewer than 1% of May 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 May air quality problems?▾
Fine particulate matter (PM2.5) set the daily AQI on 52.5% of May days in Louisville. The highest May AQI recorded in 2019–2025 was 108 (Unhealthy for Sensitive Groups), in 2023.
Louisville May air quality, year by year
Louisville May 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 | 55 | 0 | 93 | PM2.5 |
| 2020 | 31 | 47 | 0 | 61 | PM2.5 |
| 2021 | 31 | 51 | 1 | 108 | O3 |
| 2022 | 31 | 51 | 0 | 97 | PM2.5 |
| 2023worst | 31 | 55 | 1 | 101 | O3 |
| 2024 | 31 | 49 | 0 | 97 | O3 |
| 2025cleanest | 31 | 43 | 0 | 71 | O3 |
What May air means in Louisville
A typical May day in Louisville is Moderate (median AQI 51): outdoor exercise is acceptable for most people, but unusually sensitive individuals should watch for symptoms, and fewer than 1% of May days reached AQI 101+ — the level at which EPA advises people with asthma, children and older adults to shorten hard outdoor exertion.
May's median AQI of 51 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 May AQI across every EPA metro area (104,064 metro-days, 2019–2025) is 44, so Louisville runs above the national May norm; 0.9% of its May days topped AQI 100 versus 1.3% nationally (about the same).
May is part of Louisville's spring season (March, April, May); the spring 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 61 (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.