Bad Air Days in Horry County, South Carolina: under 1 a Year
under 1 bad air days a year
Rare: among the cleanest-air counties EPA monitors. Ranked 835 of 996 monitored counties, where 1 is worst.
What makes them bad: mostly particles: smoke and dust (100% particle days).
Which months to watch
- J
- F
- M
- A
- M
- J
- J
- A
- S
- O
- N
- D
Most bad days here fall in March. 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.
Better or worse than it was
The worst recent year was 2025, with 3 bad days on 325 monitored days.
| Date | AQI | Main pollutant |
|---|---|---|
| 2025-03-02 | 170 | PM2.5 |
| 2025-03-28 | 156 | PM2.5 |
| 2025-03-03 | 122 | PM2.5 |
| 2023-04-19 | 100 | Ozone |
| 2023-06-10 | 100 | Ozone |
An ordinary day in Horry
Across 2,533 monitored days from 2016 to 2025, the air in Horry County rated Good on 88% of them, more often than the 72% typical of monitored counties, and Moderate on 11%. The median day sat at AQI 37; one day in ten went above 50.
The pollutant setting the AQI on an ordinary day here:
- ozone78%1,987 days
- fine particles (PM2.5)22%546 days
Horry County by year
| Year | Days monitored | Good | Moderate | Over 100 | Over 150 | Median AQI | Highest AQI |
|---|---|---|---|---|---|---|---|
| 2025* | 325 | 268 | 54 | 3 | 2 | 39 | 170 |
| 2024 | 364 | 287 | 77 | 0 | 0 | 40 | 87 |
| 2023 | 332 | 238 | 94 | 0 | 0 | 43 | 100 |
| 2022 | 263 | 247 | 16 | 0 | 0 | 38 | 93 |
| 2021 | 264 | 238 | 26 | 0 | 0 | 38 | 90 |
| 2020 | 214 | 214 | 0 | 0 | 0 | 32 | 50 |
| 2019 | 101 | 99 | 2 | 0 | 0 | 35 | 77 |
| 2018 | 180 | 164 | 16 | 0 | 0 | 37 | 87 |
| 2017 | 354 | 350 | 4 | 0 | 0 | 32 | 64 |
| 2016 | 136 | 136 | 0 | 0 | 0 | 26 | 39 |
| 2011 | 259 | 225 | 34 | 0 | 0 | 41 | 90 |
| 2010 | 239 | 204 | 34 | 1 | 0 | 41 | 101 |
*2025 may be a partial year in EPA's file.
Nearby counties on file
- Cherokee Countythin data
- York County2/yr
- Spartanburg County2/yr
- Richland County1/yr
- Colleton County1/yr
- Greenville County1/yr
- Charleston Countyunder 1/yr
- Chesterfield 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.