Bad Air Days in Duchesne County, Utah: 10 a Year
10 bad air days a year
Among the worst tenth of monitored US counties. Ranked 89 of 996 monitored counties, where 1 is worst.
What makes them bad: mostly ozone: summer smog (19% 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 February. Averaged over 2016 to 2025.
Is a purifier worth it here?
- Ozone drives many bad days here. Purifiers and filters do not remove ozone, so do not buy one for that. Ozone peaks on hot afternoons: exercise outside in the morning.
The worst days on file
The worst recent year was 2023, with 34 bad days on 365 monitored days.
| Date | AQI | Main pollutant |
|---|---|---|
| 2023-02-05 | 215 | Ozone |
| 2023-02-12 | 190 | Ozone |
| 2023-02-04 | 185 | Ozone |
| 2023-02-26 | 185 | Ozone |
| 2016-02-13 | 177 | Ozone |
An ordinary day in Duchesne
Across 3,653 monitored days from 2016 to 2025, the air in Duchesne County rated Good on 62% of them, less often than the 72% typical of monitored counties, and Moderate on 35%. The median day sat at AQI 47; one day in ten went above 74.
The pollutant setting the AQI on an ordinary day here:
- ozone81%2,977 days
- fine particles (PM2.5)18%655 days
- coarse dust (PM10)1%19 days
Year by year
| Year | Days monitored | Good | Moderate | Over 100 | Over 150 | Median AQI | Highest AQI |
|---|---|---|---|---|---|---|---|
| 2025* | 365 | 218 | 145 | 2 | 0 | 46 | 112 |
| 2024 | 366 | 225 | 136 | 5 | 2 | 47 | 165 |
| 2023 | 365 | 180 | 151 | 34 | 12 | 51 | 215 |
| 2022 | 365 | 223 | 138 | 4 | 1 | 48 | 177 |
| 2021 | 365 | 220 | 137 | 8 | 1 | 48 | 155 |
| 2020 | 366 | 239 | 122 | 5 | 0 | 46 | 125 |
| 2019 | 365 | 226 | 128 | 11 | 4 | 48 | 177 |
| 2018 | 365 | 209 | 145 | 11 | 0 | 47 | 129 |
| 2017 | 365 | 261 | 95 | 9 | 3 | 45 | 156 |
| 2016 | 366 | 268 | 90 | 8 | 3 | 45 | 177 |
| 2015 | 365 | 269 | 93 | 3 | 0 | 45 | 129 |
| 2014 | 365 | 268 | 95 | 2 | 0 | 46 | 119 |
| 2013 | 365 | 171 | 150 | 44 | 27 | 51 | 213 |
| 2012 | 366 | 206 | 151 | 9 | 0 | 48 | 146 |
| 2011 | 365 | 207 | 135 | 23 | 6 | 49 | 220 |
*2025 may be a partial year in EPA's file.
Elsewhere in Utah
- Salt Lake County30/yr
- Davis County15/yr
- Uintah County13/yr
- Weber County11/yr
- Utah County10/yr
- Cache County8/yr
- Tooele County8/yr
- Box Elder 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, and on why a purifier does not touch ozone in smoke vs ozone.