Bad Air Days in Teton County, Montana: under 1 a Year
under 1 bad air day a year
Rare: among the cleanest-air counties EPA monitors. Ranked 775 of 996 monitored counties, where 1 is worst.
What makes them bad: mostly particles: smoke and dust (100% 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. Averaged over 2016 to 2025.
Is a purifier worth it here?
- 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 record for Teton
The worst recent year was 2024, with 1 bad day on 310 monitored days.
| Date | AQI | Main pollutant |
|---|---|---|
| 2024-07-22 | 101 | PM2.5 |
| 2024-09-09 | 96 | PM2.5 |
| 2025-07-15 | 92 | PM2.5 |
| 2025-06-11 | 89 | PM2.5 |
| 2025-06-12 | 88 | PM2.5 |
Most days, not the worst ones
Across 587 monitored days from 2024 to 2025, the air in Teton County rated Good on 95% of them, more often than the 72% typical of monitored counties, and Moderate on 5%. The median day sat at AQI 13; one day in ten went above 36.
The pollutant setting the AQI on an ordinary day here:
- fine particles (PM2.5)100%587 days
Year by year
| Year | Days monitored | Good | Moderate | Over 100 | Over 150 | Median AQI | Highest AQI |
|---|---|---|---|---|---|---|---|
| 2025* | 277 | 269 | 8 | 0 | 0 | 12 | 92 |
| 2024 | 310 | 286 | 23 | 1 | 0 | 13 | 101 |
*2025 may be a partial year in EPA's file.
Elsewhere in Montana
- Missoula County18/yr
- Ravalli County11/yr
- Lewis and Clark County9/yr
- Lincoln County8/yr
- Silver Bow County7/yr
- Sanders County7/yr
- Powder River County6/yr
- Flathead County6/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.