Bad Air Days in Franklin County, Idaho: 4 a Year
4 bad air days a year
About the middle of monitored US counties. Ranked 262 of 996 monitored counties, where 1 is worst.
What makes them bad: mostly particles: smoke and dust (100% particle days).
When the bad days come in Franklin
- J
- F
- M
- A
- M
- J
- J
- A
- S
- O
- N
- D
Most bad days here fall in January and February and August and December. Averaged over 2016 to 2025.
Is a purifier worth it 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 2017, with 14 bad days on 365 monitored days.
| Date | AQI | Main pollutant |
|---|---|---|
| 2017-02-02 | 172 | PM2.5 |
| 2020-08-21 | 162 | PM2.5 |
| 2017-02-01 | 160 | PM2.5 |
| 2017-02-03 | 160 | PM2.5 |
| 2023-02-04 | 155 | PM2.5 |
Most days, not the worst ones
Across 3,570 monitored days from 2016 to 2025, the air in Franklin County rated Good on 82% of them, more often than the 72% typical of monitored counties, and Moderate on 17%. The median day sat at AQI 26; one day in ten went above 58.
The pollutant setting the AQI on an ordinary day here:
- fine particles (PM2.5)100%3,570 days
Year by year
| Year | Days monitored | Good | Moderate | Over 100 | Over 150 | Median AQI | Highest AQI |
|---|---|---|---|---|---|---|---|
| 2025* | 351 | 338 | 13 | 0 | 0 | 21 | 82 |
| 2024 | 358 | 304 | 54 | 0 | 0 | 22 | 88 |
| 2023 | 361 | 310 | 47 | 4 | 1 | 24 | 155 |
| 2022 | 365 | 310 | 54 | 1 | 0 | 23 | 103 |
| 2021 | 365 | 285 | 74 | 6 | 0 | 28 | 119 |
| 2020 | 365 | 297 | 65 | 3 | 1 | 26 | 162 |
| 2019 | 364 | 315 | 46 | 3 | 0 | 23 | 112 |
| 2018 | 319 | 249 | 67 | 3 | 0 | 25 | 124 |
| 2017 | 365 | 239 | 112 | 14 | 5 | 37 | 172 |
| 2016 | 357 | 271 | 79 | 7 | 0 | 34 | 125 |
| 2015 | 335 | 285 | 45 | 5 | 1 | 28 | 170 |
| 2014 | 359 | 318 | 39 | 2 | 0 | 25 | 105 |
| 2013 | 357 | 259 | 66 | 32 | 11 | 30 | 184 |
| 2012 | 366 | 244 | 118 | 4 | 0 | 42 | 125 |
| 2011 | 312 | 227 | 76 | 9 | 5 | 38 | 172 |
| 2010 | 33 | 9 | 21 | 3 | 1 | 58 | 161 |
*2025 may be a partial year in EPA's file.
Idaho compared
- Lemhi County15/yr
- Ada County12/yr
- Benewah County10/yr
- Boise County10/yr
- Shoshone County8/yr
- Canyon County7/yr
- Nez Perce County7/yr
- Idaho County7/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.