Best Cities for Air Quality in Connecticut
Ranking of cities with the cleanest air in Connecticut based on AQI data.
Cleanest air in Connecticut: New Haven
Of the 2 Connecticut metro areas EPA published a full year of AQI data for in 2025, New Haven recorded the highest share of Good-air days: 245 of 365 monitored days (67.1%) at AQI 50 or below, with a median AQI of 43 and 13 days above AQI 100. Its peak reading that year was AQI 159. The pollutant that set the daily AQI most often was ground-level ozone (226 days). The other end of the Connecticut list is Hartford (66.6% Good days, median AQI 42, 11 days above AQI 100).
| # | City (EPA area) | Good days (2025) | Median AQI | Days over 100 | Peak AQI | AQI now |
|---|---|---|---|---|---|---|
| 1 | New HavenNew Haven-Milford, CT | 245 / 365 (67.1%) | 43 | 13 | 159 | 15 |
| 2 | HartfordHartford-West Hartford-East Hartford, CT | 243 / 365 (66.6%) | 42 | 11 | 164 | 15 |
Figures are EPA's published annual AQI summaries by metropolitan area (Annual AQI by CBSA, 2019–2025), retrieved 2026-09-07. The daily AQI EPA summarises is the highest value any monitor in the area reported that day, so these are metro-area readings, not statewide or rural ones.
New Haven's air quality year by year
One clean year can be luck — a mild summer, no wildfire smoke. This is every year EPA has published for the New Haven-Milford, CT area, so you can see whether New Haven's ranking is durable.
| Year | Days measured | Good days | Median AQI | Days over 100 | Days over 150 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|---|---|
| 2019 | 365 | 228 | 44 | 14 | 2 | 159 | ground-level ozone |
| 2020 | 366 | 210 | 46 | 13 | 2 | 174 | fine particulate matter (PM2.5) |
| 2021 | 365 | 220 | 46 | 14 | 2 | 159 | fine particulate matter (PM2.5) |
| 2022 | 365 | 230 | 44 | 7 | 0 | 133 | fine particulate matter (PM2.5) |
| 2023 | 365 | 205 | 47 | 12 | 3 | 208 | fine particulate matter (PM2.5) |
| 2024 | 366 | 260 | 41 | 12 | 1 | 156 | ground-level ozone |
| 2025 | 365 | 245 | 43 | 13 | 2 | 159 | ground-level ozone |
Across 2019–2025, New Haven's air quality shows no clear trend: the area's median AQI held near 45 and days above AQI 100 fell from about 14 to 12 per year (comparing the earlier and later halves of the period).
How Connecticut compares
Ranked by the median of its metro areas' median AQI in 2025, Connecticut is #17 cleanest of the 51 states EPA publishes metro AQI data for, at a median AQI of 43. The cleanest state on that measure is Alaska; the most polluted is Arizona. See the full state air quality rankings.
| Bordering state | Median metro AQI (2025) | National rank (cleanest first) |
|---|---|---|
| Massachusetts | 40 | #9 of 51 |
| New York | 41 | #12 of 51 |
| Rhode Island | 43 | #15 of 51 |
What this ranking does and does not cover
We track 2 Connecticut cities. 2 have a full 2025 EPA record and are ranked above.
EPA's AQI is reported by metropolitan area, and the daily value is the worst reading from any monitor in that area. Rural Connecticut — and any town without a regulatory monitor — is not represented here. A high Good-day share means the monitored metro air was clean on most days; it is not a statement about a specific street, and it does not capture short pollution spikes between the daily summaries.