Bad Air Days in Billings County, North Dakota: 4 a Year
4 bad air days a year
About the middle of monitored US counties. Ranked 317 of 996 monitored counties, where 1 is worst.
What makes them bad: mostly particles: smoke and dust (86% particle days).
Which months to watch
- J
- F
- M
- A
- M
- J
- J
- A
- S
- O
- N
- D
Most bad days here fall in July and September and May and June and August. 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.
- Upgrade the furnace or AC filter to MERV 13 so the whole house is filtered, not just one room.
The worst days on file
In 2000 to 2009 this county averaged under 1 bad days a year; in 2016 to 2025, 4. It has got worse. The worst recent year was 2023, with 10 bad days on 365 monitored days.
| Date | AQI | Main pollutant |
|---|---|---|
| 2023-05-17 | 226 | PM2.5 |
| 2025-06-11 | 195 | PM2.5 |
| 2025-07-12 | 195 | PM2.5 |
| 2025-08-10 | 190 | PM2.5 |
| 2024-09-10 | 172 | PM2.5 |
Most days, not the worst ones
Across 3,644 monitored days from 2016 to 2025, the air in Billings County rated Good on 87% of them, more often than the 72% typical of monitored counties, and Moderate on 12%. The median day sat at AQI 37; one day in ten went above 54.
The pollutant setting the AQI on an ordinary day here:
- ozone79%2,885 days
- fine particles (PM2.5)21%759 days
Billings County by year
| Year | Days monitored | Good | Moderate | Over 100 | Over 150 | Median AQI | Highest AQI |
|---|---|---|---|---|---|---|---|
| 2025* | 364 | 301 | 55 | 8 | 4 | 38 | 195 |
| 2024 | 366 | 303 | 53 | 10 | 1 | 38 | 172 |
| 2023 | 365 | 282 | 73 | 10 | 3 | 39 | 226 |
| 2022 | 363 | 323 | 40 | 0 | 0 | 39 | 79 |
| 2021 | 364 | 299 | 60 | 5 | 2 | 37 | 161 |
| 2020 | 366 | 346 | 20 | 0 | 0 | 35 | 65 |
| 2019 | 365 | 346 | 19 | 0 | 0 | 34 | 84 |
| 2018 | 361 | 311 | 50 | 0 | 0 | 38 | 90 |
| 2017 | 364 | 322 | 40 | 2 | 1 | 37 | 156 |
| 2016 | 366 | 353 | 13 | 0 | 0 | 35 | 92 |
| 2015 | 365 | 303 | 58 | 4 | 1 | 37 | 154 |
| 2014 | 365 | 357 | 8 | 0 | 0 | 36 | 63 |
| 2013 | 365 | 345 | 20 | 0 | 0 | 38 | 77 |
| 2012 | 354 | 333 | 21 | 0 | 0 | 35 | 67 |
| 2011 | 323 | 307 | 16 | 0 | 0 | 39 | 64 |
| 2010 | 354 | 334 | 20 | 0 | 0 | 38 | 90 |
*2025 may be a partial year in EPA's file.
North Dakota compared
- Burleigh County7/yr
- Ward County7/yr
- Oliver County6/yr
- Burke County6/yr
- Dunn County5/yr
- Cass County5/yr
- Mercer County5/yr
- McKenzie County4/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.