Bad Air Days in Iron County, Utah: under 1 a Year
under 1 bad air day a year
Fewer bad air days than most monitored US counties. Ranked 738 of 996 monitored counties, where 1 is worst.
What makes them bad: a mix of particles and ozone (50% particle days).
Which months to watch
- J
- F
- M
- A
- M
- J
- J
- A
- S
- O
- N
- D
Most bad days here fall in August and June and March. 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.
The worst days on file
The worst recent year was 2021, with 4 bad days on 365 monitored days.
| Date | AQI | Main pollutant |
|---|---|---|
| 2021-08-07 | 176 | PM2.5 |
| 2025-06-20 | 105 | Ozone |
| 2021-08-08 | 104 | PM2.5 |
| 2023-03-06 | 103 | NO2 |
| 2021-08-16 | 102 | PM2.5 |
An ordinary day in Iron
Across 2,920 monitored days from 2018 to 2025, the air in Iron County rated Good on 81% of them, more often than the 72% typical of monitored counties, and Moderate on 19%. The median day sat at AQI 42; one day in ten went above 58.
The pollutant setting the AQI on an ordinary day here:
- ozone81%2,375 days
- fine particles (PM2.5)16%469 days
- nitrogen dioxide3%76 days
Iron County by year
| Year | Days monitored | Good | Moderate | Over 100 | Over 150 | Median AQI | Highest AQI |
|---|---|---|---|---|---|---|---|
| 2025* | 364 | 272 | 91 | 1 | 0 | 44 | 105 |
| 2024 | 365 | 303 | 62 | 0 | 0 | 43 | 100 |
| 2023 | 365 | 309 | 55 | 1 | 0 | 42 | 103 |
| 2022 | 365 | 309 | 56 | 0 | 0 | 42 | 80 |
| 2021 | 365 | 286 | 75 | 4 | 1 | 40 | 176 |
| 2020 | 366 | 312 | 54 | 0 | 0 | 41 | 88 |
| 2019 | 365 | 320 | 45 | 0 | 0 | 43 | 84 |
| 2018 | 365 | 257 | 108 | 0 | 0 | 44 | 90 |
*2025 may be a partial year in EPA's file.
Nearby counties on file
- Salt Lake County30/yr
- Davis County15/yr
- Uintah County13/yr
- Weber County11/yr
- Utah County10/yr
- Duchesne County10/yr
- Cache County8/yr
- Tooele County8/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.