Bad Air Days in Brown County, South Dakota: 3 a Year
3 bad air days a year
About the middle of monitored US counties. Ranked 355 of 996 monitored counties, where 1 is worst.
What makes them bad: mostly particles: smoke and dust (100% 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 August and September. Averaged over 2016 to 2025.
What actually helps here
- Particles (wildfire smoke, dust) cause enough bad days here to matter. A HEPA purifier sized to your bedroom removes them; run it with windows shut on bad days.
Better or worse than it was
The worst recent year was 2023, with 8 bad days on 365 monitored days.
| Date | AQI | Main pollutant |
|---|---|---|
| 2018-06-01 | 421 | PM10 |
| 2021-07-30 | 208 | PM2.5 |
| 2023-05-18 | 166 | PM2.5 |
| 2021-07-29 | 162 | PM2.5 |
| 2021-07-31 | 160 | PM2.5 |
An ordinary day in Brown
Across 2,636 monitored days from 2016 to 2025, the air in Brown County rated Good on 85% of them, more often than the 72% typical of monitored counties, and Moderate on 14%. The median day sat at AQI 27; one day in ten went above 54.
The pollutant setting the AQI on an ordinary day here:
- fine particles (PM2.5)74%1,953 days
- coarse dust (PM10)26%683 days
Every recent year on file
| Year | Days monitored | Good | Moderate | Over 100 | Over 150 | Median AQI | Highest AQI |
|---|---|---|---|---|---|---|---|
| 2025* | 360 | 301 | 53 | 6 | 0 | 27 | 115 |
| 2024 | 357 | 306 | 47 | 4 | 0 | 24 | 118 |
| 2023 | 365 | 289 | 68 | 8 | 1 | 29 | 166 |
| 2022 | 350 | 325 | 25 | 0 | 0 | 23 | 93 |
| 2021 | 356 | 301 | 52 | 3 | 3 | 26 | 208 |
| 2020 | 364 | 308 | 56 | 0 | 0 | 28 | 78 |
| 2019 | 122 | 104 | 18 | 0 | 0 | 25 | 80 |
| 2018 | 121 | 104 | 15 | 2 | 1 | 32 | 421 |
| 2017 | 122 | 108 | 14 | 0 | 0 | 31 | 97 |
| 2016 | 119 | 104 | 15 | 0 | 0 | 26 | 79 |
| 2015 | 121 | 102 | 19 | 0 | 0 | 32 | 94 |
| 2014 | 119 | 103 | 16 | 0 | 0 | 29 | 85 |
| 2013 | 121 | 90 | 31 | 0 | 0 | 34 | 77 |
| 2012 | 123 | 86 | 37 | 0 | 0 | 37 | 80 |
| 2011 | 122 | 94 | 28 | 0 | 0 | 33 | 70 |
| 2010 | 119 | 80 | 39 | 0 | 0 | 41 | 92 |
*2025 may be a partial year in EPA's file.
Nearby counties on file
- Clay County6/yr
- Minnehaha County5/yr
- Pennington County4/yr
- Brookings County3/yr
- Custer County3/yr
- Codington County3/yr
- Jackson County2/yr
- Union County2/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.