Bad Air Days in Fayette County, Pennsylvania: under 1 a Year
under 1 bad air day a year
Fewer bad air days than most monitored US counties. Ranked 720 of 996 monitored counties, where 1 is worst.
What makes them bad: mostly ozone: summer smog (17% particle days).
Which months to watch
- J
- F
- M
- A
- M
- J
- J
- A
- S
- O
- N
- D
Most bad days here fall in July and April and June and August. Averaged over 2016 to 2025.
Is a purifier worth it 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 Fayette
The worst recent year was 2023, with 2 bad days on 304 monitored days.
| Date | AQI | Main pollutant |
|---|---|---|
| 2023-06-29 | 129 | Ozone |
| 2021-07-20 | 113 | PM2.5 |
| 2018-07-10 | 105 | Ozone |
| 2023-04-13 | 101 | Ozone |
| 2024-07-21 | 101 | Ozone |
Most days, not the worst ones
Across 2,642 monitored days from 2018 to 2025, the air in Fayette County rated Good on 72% of them, close to the 72% typical of monitored counties, and Moderate on 27%. The median day sat at AQI 42; one day in ten went above 60.
The pollutant setting the AQI on an ordinary day here:
- ozone54%1,415 days
- fine particles (PM2.5)46%1,225 days
Fayette County by year
| Year | Days monitored | Good | Moderate | Over 100 | Over 150 | Median AQI | Highest AQI |
|---|---|---|---|---|---|---|---|
| 2025* | 365 | 288 | 77 | 0 | 0 | 40 | 93 |
| 2024 | 366 | 269 | 95 | 2 | 0 | 42 | 101 |
| 2023 | 304 | 220 | 82 | 2 | 0 | 44 | 129 |
| 2022 | 302 | 218 | 84 | 0 | 0 | 43 | 87 |
| 2021 | 354 | 227 | 126 | 1 | 0 | 43 | 113 |
| 2020 | 363 | 265 | 98 | 0 | 0 | 42 | 100 |
| 2019 | 360 | 273 | 87 | 0 | 0 | 42 | 75 |
| 2018 | 228 | 155 | 72 | 1 | 0 | 42 | 105 |
*2025 may be a partial year in EPA's file.
Pennsylvania compared
- Allegheny County12/yr
- Philadelphia County9/yr
- Bucks County8/yr
- Warren Countythin data
- Lancaster County6/yr
- Berks County5/yr
- Delaware County4/yr
- Northampton County4/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.