Air quality in Connecticut
EPA monitors report from 8 of Connecticut’s 8 counties. That is the honest limit of this page: the other 0 are not measured, not clean. In 2025 the most affected monitored county was Fairfield County, with 21 days above the moderate category.
8
Counties with monitors
0
Counties without
71
Days above moderate, 2025
Summed across monitored counties
-
Adults with asthma
Population-weighted county estimate
County by county
Monitored Connecticut counties
GoodModerateUnhealthy for sensitive groupsUnhealthyVery unhealthyHazardous
| County | 90th %ile AQI | Above moderate | Max AQI | 2025 days by category |
|---|---|---|---|---|
| Fairfield County | 74 | 21 | 174 | |
| New Haven County | 68 | 13 | 159 | |
| Litchfield County | 64 | 9 | 161 | |
| Hartford County | 68 | 8 | 164 | |
| New London County | 60 | 8 | 136 | |
| Middlesex County | 77 | 6 | 151 | |
| Tolland County | 61 | 5 | 136 | |
| Windham County | 47 | 1 | 108 |
EPA Air Quality System annual summaries by county, 2025. The 90th percentile AQI describes a day worse than nine out of ten, which is a steadier measure than the annual maximum a single wildfire can set.
Other states
Air quality elsewhere
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