Air quality · Connecticut
Air quality in Connecticut
Across the 6 Connecticut ZIPs with EPA county air-quality data, the median day is Good in all 6 (median AQI 39–44). 11 days across those counties reached Unhealthy or worse in 2025. This is a 2025 county annual summary, not a live reading.
Last verified 2026-09-24 · methodology
Air quality by ZIP code in Connecticut
EPA's 2025 annual summary for each ZIP's county. Median AQI is the typical day; lower is cleaner.
| ZIP | Median AQI | Good days | Unhealthy or worse |
|---|---|---|---|
| 06103HartfordHartford County | 42 Good | 248 of 365 | 2 |
| 06820DarienFairfield County | 44 Good | 236 of 365 | 2 |
| 06105HartfordHartford County | 42 Good | 248 of 365 | 2 |
| 06511New HavenNew Haven County | 43 Good | 245 of 365 | 2 |
| 06880Westport (CT)Fairfield County | 44 Good | 236 of 365 | 2 |
| 06776New Milford (CT)Litchfield County | 39 Good | 297 of 365 | 1 |
County-level figures from EPA Air Quality System (AQS), annual county summary, joined to each ZIP by county. None of them is a measurement at a specific address.
What lands here
Pages show the 2025 median AQI category (Good, Moderate, Unhealthy for Sensitive Groups, Unhealthy, Very Unhealthy, Hazardous) for the ZIP's county, plus the year's max/90th-percentile AQI and day-count breakdown by category.
Source & refresh
EPA Air Quality System (AQS), annual county summary. Refreshed annual (epa aqs publication). Primary source →
Connecticut top concern
Lead service lines, coastal flood
Connecticut's older housing stock carries elevated LCRR-flagged lead service line risk in cities like Hartford, Bridgeport, New Haven. Coastal Long Island Sound communities sit in FEMA AE/VE zones with Risk Rating 2.0 premium pressure. School data via NCES splits between large municipal districts and small magnet/charter networks.
See Connecticut state page for the full state-level rollup across all 12 dimensions.
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