Smoke: keep one room clean
Shut the windows and run an air purifier sized for the room.
Wildfire smoke guide →Air quality in Connecticut, county by county
8 Connecticut counties have enough EPA monitor data to count bad-air days. Weighted by population, they averaged about 11 days a year from 2021 to 2025 when the air was unhealthy for sensitive groups or worse.
CDC's model, which estimates every county from monitors and satellites, gives the average Connecticut county, weighted by population, about 1 smoky day (fine particles over 35.4 µg/m³, mostly wildfire smoke) and about 9 high-ozone days a year at its worst spot (2018 to 2022). See every county on the map.
Every Connecticut county with monitors
Most bad-air days first. 8 have a full report. Compare with the worst and the cleanest counties in the US.
| County | Bad-air days a year | |
|---|---|---|
| Fairfield CountyOzone | 20.6 | |
| New Haven CountyOzone | 11.6 | |
| New London CountyOzone | 6.8 | |
| Middlesex CountyOzoneparticles not measured | 6.6 | |
| Litchfield CountyOzone | 6.0 | |
| Hartford CountyEast HartfordOzone | 5.8 | |
| Tolland CountyOzoneparticles not measured | 3.2 | |
| Windham CountyPutnamOzoneparticles not measured | 1.2 | |
| No Connecticut county with a monitor matches “”. Counties without a monitor aren't listed; a neighbor's numbers are a fair guide, or find it on the map. | ||
Counties without a monitor aren't listed. Air doesn't stop at the county line, so a neighbor's numbers are a fair guide.
What helps on a bad-air day
Check AirNow for today's reading and tomorrow's forecast, then match the step to the pollutant.
Upgrade the furnace filter
MERV 13 catches far more smoke than thin fiberglass filters.
Furnace filters →Questions people ask about air quality in Connecticut
Which county in Connecticut has the worst air?
Among Connecticut counties with EPA monitors, Fairfield County had the most bad-air days from 2021 to 2025: about 21 bad-air days a year with an AQI over 100. That's about 1 day in 18.
How often is the air bad in Connecticut?
Weighted by population, Connecticut counties with monitors averaged about 11 bad-air days a year from 2021 to 2025 with an AQI over 100, when children, older adults and people with asthma should cut back outdoors. That's about 1 day in 33.
Which county in Connecticut has the cleanest air?
Of the 8 counties with enough monitor data, Windham County had the fewest: 1.2 a year from 2021 to 2025. Counties without monitors aren't ranked.
Where can I check today's air quality in Connecticut?
AirNow, run by the EPA and its partners, shows current readings and forecasts by ZIP code, and its fire and smoke map adds smoke plumes and low-cost sensors.
Sources: EPA AirData county AQI summaries, 2021 to 2025; CDC Environmental Public Health Tracking Network modeled PM2.5 and ozone, 2018 to 2022. Updated November 8, 2026.