Bad Air Days in St. Martin Parish, Louisiana: under 1 a Year
under 1 bad air days a year
Rare: among the cleanest-air counties EPA monitors. Ranked 887 of 996 monitored counties, where 1 is worst.
What makes them bad: mostly ozone: summer smog (0% particle days).
Which months to watch
- J
- F
- M
- A
- M
- J
- J
- A
- S
- O
- N
- D
Most bad days here fall in September and April. Averaged over 2016 to 2025.
What to buy, and what not to
- 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 2024, with 1 bad day on 332 monitored days.
| Date | AQI | Main pollutant |
|---|---|---|
| 2023-09-01 | 112 | Ozone |
| 2017-09-14 | 101 | Ozone |
| 2024-04-05 | 101 | Ozone |
| 2017-05-07 | 100 | Ozone |
| 2016-04-05 | 97 | Ozone |
An ordinary day in St. Martin
Across 3,527 monitored days from 2016 to 2025, the air in St. Martin Parish 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 35; one day in ten went above 51.
The pollutant setting the AQI on an ordinary day here:
- ozone100%3,527 days
St. Martin Parish by year
| Year | Days monitored | Good | Moderate | Over 100 | Over 150 | Median AQI | Highest AQI |
|---|---|---|---|---|---|---|---|
| 2025* | 360 | 332 | 28 | 0 | 0 | 36 | 77 |
| 2024 | 332 | 292 | 39 | 1 | 0 | 38 | 101 |
| 2023 | 364 | 316 | 47 | 1 | 0 | 37 | 112 |
| 2022 | 338 | 296 | 42 | 0 | 0 | 34 | 97 |
| 2021 | 360 | 347 | 13 | 0 | 0 | 34 | 87 |
| 2020 | 358 | 337 | 21 | 0 | 0 | 33 | 87 |
| 2019 | 355 | 330 | 25 | 0 | 0 | 34 | 80 |
| 2018 | 352 | 321 | 31 | 0 | 0 | 33 | 97 |
| 2017 | 347 | 318 | 28 | 1 | 0 | 36 | 101 |
| 2016 | 361 | 324 | 37 | 0 | 0 | 39 | 97 |
| 2015 | 65 | 59 | 6 | 0 | 0 | 38 | 84 |
*2025 may be a partial year in EPA's file.
Louisiana compared
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.