Smoke: keep one room clean
Shut the windows and run an air purifier sized for the room.
Wildfire smoke guide →Air quality in Maine, county by county
11 Maine counties have enough EPA monitor data to count bad-air days. Weighted by population, they averaged about 2 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 Maine county, weighted by population, almost no smoky days (fine particles over 35.4 µg/m³, mostly wildfire smoke) and almost no high-ozone days a year at its worst spot (2018 to 2022). See every county on the map.
Every Maine county with monitors
Most bad-air days first. 9 have a full report. Compare with the worst and the cleanest counties in the US.
| County | Bad-air days a year | |
|---|---|---|
| Cumberland CountyPortlandOzone and particles | 3.0 | |
| Aroostook CountySummer smoke | 1.8 | |
| Hancock CountyOzone | 1.8 | |
| York CountySanfordOzoneparticles not measured | 1.8 | |
| Penobscot CountyBangorSummer smoke | 1.2 | |
| Oxford CountySummer smoke | 0.8 | |
| Androscoggin CountyLewistonRarely bad | 0.4 | |
| Knox CountyRarely badparticles not measured | 0.4 | |
| Sagadahoc CountyRarely badparticles not measured | 0.3 | |
| Kennebec CountyAugustaRarely bad | 0.2 | |
| Washington CountyRarely bad | 0.0 | |
| No Maine 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 Maine
Which county in Maine has the worst air?
Among Maine counties with EPA monitors, Cumberland County had the most bad-air days from 2021 to 2025: about 3 bad-air days a year with an AQI over 100.
How often is the air bad in Maine?
Weighted by population, Maine counties with monitors averaged about 2 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.
Which county in Maine has the cleanest air?
Of the 11 counties with enough monitor data, Washington County had the fewest, with no bad-air days at all from 2021 to 2025. Counties without monitors aren't ranked.
Where can I check today's air quality in Maine?
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.