Bad Air Days in Kennebec County, Maine: under 1 a Year
under 1 bad air days a year
Rare: among the cleanest-air counties EPA monitors. Ranked 935 of 996 monitored counties, where 1 is worst.
What makes them bad: mostly ozone: summer smog (0% particle days).
The bad-air season here
- J
- F
- M
- A
- M
- J
- J
- A
- S
- O
- N
- D
Most bad days here fall in July. Averaged over 2016 to 2025.
What actually helps here
- Bad air days are rare here. A standard furnace filter is enough; no purifier needed for outdoor air.
- On the odd bad day, check AirNow and keep windows shut.
The record for Kennebec
In 2000 to 2009 this county averaged 8 bad days a year; in 2016 to 2025, under 1. The air has improved. The worst recent year was 2021, with 1 bad day on 244 monitored days.
| Date | AQI | Main pollutant |
|---|---|---|
| 2021-07-23 | 125 | Ozone |
| 2017-04-11 | 100 | Ozone |
| 2017-05-17 | 97 | Ozone |
| 2025-07-26 | 96 | PM2.5 |
| 2025-08-04 | 96 | PM2.5 |
The air on a normal day
Across 3,097 monitored days from 2016 to 2025, the air in Kennebec County rated Good on 91% of them, more often than the 72% typical of monitored counties, and Moderate on 9%. The median day sat at AQI 32; one day in ten went above 49.
The pollutant setting the AQI on an ordinary day here:
- ozone60%1,864 days
- fine particles (PM2.5)26%799 days
- nitrogen dioxide14%423 days
Every recent year on file
| Year | Days monitored | Good | Moderate | Over 100 | Over 150 | Median AQI | Highest AQI |
|---|---|---|---|---|---|---|---|
| 2025* | 365 | 311 | 54 | 0 | 0 | 34 | 96 |
| 2024 | 366 | 310 | 56 | 0 | 0 | 35 | 77 |
| 2023 | 299 | 242 | 57 | 0 | 0 | 37 | 92 |
| 2022 | 203 | 194 | 9 | 0 | 0 | 30 | 84 |
| 2021 | 244 | 226 | 17 | 1 | 0 | 33 | 125 |
| 2020 | 230 | 221 | 9 | 0 | 0 | 35 | 67 |
| 2019 | 361 | 352 | 9 | 0 | 0 | 29 | 70 |
| 2018 | 360 | 339 | 21 | 0 | 0 | 30 | 90 |
| 2017 | 360 | 342 | 18 | 0 | 0 | 31 | 100 |
| 2016 | 309 | 291 | 18 | 0 | 0 | 31 | 84 |
| 2015 | 237 | 216 | 21 | 0 | 0 | 36 | 93 |
| 2014 | 286 | 279 | 7 | 0 | 0 | 29 | 87 |
| 2013 | 361 | 349 | 11 | 1 | 0 | 30 | 108 |
| 2012 | 308 | 297 | 11 | 0 | 0 | 29 | 90 |
| 2011 | 211 | 195 | 16 | 0 | 0 | 31 | 97 |
| 2010 | 237 | 222 | 14 | 1 | 0 | 36 | 129 |
*2025 may be a partial year in EPA's file.
Maine compared
- York County2/yr
- Hancock County2/yr
- Cumberland County2/yr
- Aroostook County2/yr
- Knox County1/yr
- Penobscot Countyunder 1/yr
- Sagadahoc Countyunder 1/yr
- Oxford Countyunder 1/yr
How this is counted
A bad air day is a day the county's daily AQI from EPA AirData went above 100, the level where EPA tells children, older adults and people with asthma or heart disease to cut back outdoors. Monitors do not run every day, so yearly counts are scaled to 365 days. This is the record, not today's air: for that, check AirNow. More on the method in how the county numbers are made, on the AQI 100 line in what counts as a bad air day, and on why a purifier does not touch ozone in smoke vs ozone.