Air Quality Rankings for Connecticut 2026
Connecticut has 8 cities with EPA air quality data. Windham, Connecticut has the cleanest air with a 5-year average AQI of 35. Fairfield, Connecticut has the highest AQI at 46.
| # | City | 5yr Avg AQI | Current AQI | Worst Pollutant | Trend | Grade |
|---|---|---|---|---|---|---|
| 1 | Windham, Connecticut | 35 | 34 | Ozone | Stable | B |
| 2 | Litchfield, Connecticut | 38 | 38 | Ozone | Improving | B |
| 3 | New London, Connecticut | 40 | 41 | PM2.5 | Stable | C |
| 4 | Tolland, Connecticut | 40 | 41 | Ozone | Stable | B |
| 5 | Middlesex, Connecticut | 40 | 43 | Ozone | Stable | B |
| 6 | Hartford, Connecticut | 42 | 43 | PM2.5 | Improving | B |
| 7 | New Haven, Connecticut | 45 | 47 | PM2.5 | Improving | C |
| 8 | Fairfield, Connecticut | 46 | 46 | PM2.5 | Improving | C |
Air quality data for Connecticut is sourced from the EPA Air Quality System (AQS), which monitors outdoor air quality at thousands of stations nationwide.
Frequently Asked Questions
Windham, Connecticut has the best air quality in Connecticut with a 5-year average AQI of 35 and a grade of B.
Connecticut has 8 cities with EPA air quality monitoring data in our database, covering multiple years of AQI measurements.
The Air Quality Index (AQI) measures five major pollutants: ground-level ozone, particulate matter (PM2.5 and PM10), carbon monoxide, sulfur dioxide, and nitrogen dioxide. Lower AQI values indicate cleaner air — 0-50 is "Good," while 150+ is "Unhealthy."
Cities ranked by 5-year average AQI (lower is better). Grades factor in average AQI, trend direction, unhealthy days, and dominant pollutant.