Air Quality Rankings for Kentucky (2026)

Kentucky has 27 cities tracked by EPA air-quality monitors, with a state-wide 5-year median AQI of 42 — roughly matching the national average of AQI 41. Morgan, Kentucky ranks #1 with the cleanest air (AQI 35, Grade B), while Jefferson, Kentucky sits at the bottom (AQI 54, Grade C). The rankings below are computed from the EPA Air Quality System (AQS), which aggregates daily AQI readings from federally certified monitors into annual averages. Cities are sorted by 5-year median AQI (lowest = cleanest = #1). The 5-year window smooths out year-to-year volatility from weather and wildfire events.

Air quality across Kentucky has held roughly steady over the past decade — 11 cities improving, 6 worsening, and 10 stable. That stability makes the state-average ranking a reliable signal of what residents can expect over time.

The dominant pollutant across 16 of 27 Kentucky cities is Ground-Level Ozone. Ground-level ozone forms when sunlight reacts with vehicle and industrial emissions. It is worst on hot, sunny, stagnant summer days and is the leading air quality concern across much of the Sun Belt and California. Other Kentucky cities report Fine Particulate Matter (PM2.5) (11) as their dominant concern.

The fastest-improving city in Kentucky is Pike, Kentucky, with median AQI falling by 1.6 points per year. Steady improvement at that pace usually reflects fleet turnover (older diesels retiring), upwind power-plant retirements, or tighter regional emissions controls.

The city with the steepest decline is Henderson, Kentucky, where median AQI is rising by 1.5 points per year. Rapid deterioration in a single city usually points to either wildfire-smoke exposure (in the West) or a new local emissions source — a power plant, port, or freight corridor coming online.