Bad Air Days in Harrison County, Mississippi: 1 a Year
1 bad air day a year
Fewer bad air days than most monitored US counties. Ranked 639 of 996 monitored counties, where 1 is worst.
What makes them bad: mostly ozone: summer smog (17% particle days).
When the bad days come in Harrison
- J
- F
- M
- A
- M
- J
- J
- A
- S
- O
- N
- D
Most bad days here fall in May and June and October. 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 worst days on file
In 2000 to 2009 this county averaged 22 bad days a year; in 2016 to 2025, 1. The air has improved. The worst recent year was 2024, with 5 bad days on 361 monitored days.
| Date | AQI | Main pollutant |
|---|---|---|
| 2024-10-18 | 157 | PM2.5 |
| 2018-05-09 | 115 | Ozone |
| 2018-05-17 | 115 | Ozone |
| 2024-06-13 | 115 | Ozone |
| 2024-10-13 | 115 | Ozone |
Most days, not the worst ones
Across 3,610 monitored days from 2016 to 2025, the air in Harrison County rated Good on 60% of them, less often than the 72% typical of monitored counties, and Moderate on 39%. The median day sat at AQI 46; one day in ten went above 62.
The pollutant setting the AQI on an ordinary day here:
- fine particles (PM2.5)74%2,680 days
- ozone26%930 days
Year by year
| Year | Days monitored | Good | Moderate | Over 100 | Over 150 | Median AQI | Highest AQI |
|---|---|---|---|---|---|---|---|
| 2025* | 365 | 252 | 113 | 0 | 0 | 43 | 97 |
| 2024 | 361 | 239 | 117 | 5 | 1 | 44 | 157 |
| 2023 | 361 | 166 | 193 | 2 | 0 | 51 | 105 |
| 2022 | 365 | 211 | 154 | 0 | 0 | 46 | 100 |
| 2021 | 359 | 221 | 138 | 0 | 0 | 45 | 87 |
| 2020 | 352 | 179 | 172 | 1 | 0 | 49 | 101 |
| 2019 | 363 | 201 | 162 | 0 | 0 | 47 | 97 |
| 2018 | 364 | 223 | 138 | 3 | 0 | 45 | 115 |
| 2017 | 361 | 232 | 128 | 1 | 0 | 44 | 105 |
| 2016 | 359 | 256 | 103 | 0 | 0 | 44 | 97 |
| 2015 | 363 | 223 | 138 | 2 | 0 | 44 | 115 |
| 2014 | 361 | 184 | 172 | 5 | 0 | 50 | 119 |
| 2013 | 357 | 212 | 145 | 0 | 0 | 47 | 90 |
| 2012 | 362 | 189 | 168 | 5 | 0 | 49 | 136 |
| 2011 | 361 | 142 | 212 | 7 | 0 | 53 | 129 |
| 2010 | 362 | 133 | 219 | 10 | 0 | 54 | 136 |
*2025 may be a partial year in EPA's file.
Elsewhere in Mississippi
- DeSoto County2/yr
- Jackson Countyunder 1/yr
- Hinds Countyunder 1/yr
- Bolivar Countyunder 1/yr
- Forrest Countyunder 1/yr
- Lee Countyunder 1/yr
- Hancock Countyunder 1/yr
- Yalobusha 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.