Bad Air Days in York County, South Carolina: 2 a Year
2 bad air days a year
Fewer bad air days than most monitored US counties. Ranked 545 of 996 monitored counties, where 1 is worst.
What makes them bad: mostly ozone: summer smog (6% 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 and June. 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 worst days on file
In 2000 to 2009 this county averaged 21 bad days a year; in 2016 to 2025, 2. The air has improved. The worst recent year was 2019, with 7 bad days on 365 monitored days.
| Date | AQI | Main pollutant |
|---|---|---|
| 2019-07-27 | 133 | Ozone |
| 2022-06-21 | 126 | Ozone |
| 2019-07-03 | 119 | Ozone |
| 2018-06-07 | 115 | Ozone |
| 2018-07-11 | 115 | Ozone |
The air on a normal day
Across 3,529 monitored days from 2016 to 2025, the air in York County rated Good on 73% of them, close to the 72% typical of monitored counties, and Moderate on 26%. The median day sat at AQI 43; one day in ten went above 59.
The pollutant setting the AQI on an ordinary day here:
- ozone57%2,024 days
- fine particles (PM2.5)43%1,505 days
York County by year
| Year | Days monitored | Good | Moderate | Over 100 | Over 150 | Median AQI | Highest AQI |
|---|---|---|---|---|---|---|---|
| 2025* | 361 | 276 | 85 | 0 | 0 | 43 | 93 |
| 2024 | 363 | 226 | 136 | 1 | 0 | 46 | 112 |
| 2023 | 365 | 213 | 149 | 3 | 0 | 47 | 115 |
| 2022 | 363 | 253 | 109 | 1 | 0 | 44 | 126 |
| 2021 | 360 | 257 | 103 | 0 | 0 | 44 | 97 |
| 2020 | 366 | 303 | 63 | 0 | 0 | 39 | 93 |
| 2019 | 365 | 210 | 148 | 7 | 0 | 47 | 133 |
| 2018 | 354 | 271 | 80 | 3 | 0 | 39 | 115 |
| 2017 | 307 | 275 | 31 | 1 | 0 | 38 | 105 |
| 2016 | 325 | 295 | 29 | 1 | 0 | 39 | 105 |
| 2015 | 337 | 321 | 16 | 0 | 0 | 33 | 100 |
| 2014 | 277 | 270 | 7 | 0 | 0 | 33 | 100 |
| 2013 | 251 | 227 | 24 | 0 | 0 | 38 | 87 |
| 2012 | 240 | 196 | 41 | 3 | 0 | 41 | 143 |
| 2011 | 268 | 242 | 26 | 0 | 0 | 38 | 97 |
| 2010 | 296 | 263 | 33 | 0 | 0 | 35 | 97 |
*2025 may be a partial year in EPA's file.
South Carolina compared
- Cherokee Countythin data
- Spartanburg County2/yr
- Richland County1/yr
- Colleton County1/yr
- Greenville County1/yr
- Charleston Countyunder 1/yr
- Chesterfield Countyunder 1/yr
- Edgefield 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.