Bad Air Days in Dawson County, Montana: 3 a Year
3 bad air days a year
About the middle of monitored US counties. Ranked 338 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 Dawson
- J
- F
- M
- A
- M
- J
- J
- A
- S
- O
- N
- D
Most bad days here fall in September and May and June and July and August. Averaged over 2016 to 2025.
What to buy, and what not to
- 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.
Better or worse than it was
The worst recent year was 2025, with 3 bad days on 300 monitored days.
| Date | AQI | Main pollutant |
|---|---|---|
| 2025-08-10 | 165 | PM2.5 |
| 2025-06-11 | 162 | PM2.5 |
| 2024-05-12 | 120 | PM2.5 |
| 2024-09-09 | 113 | PM2.5 |
| 2024-09-04 | 104 | PM2.5 |
Most days, not the worst ones
Across 657 monitored days from 2024 to 2025, the air in Dawson County rated Good on 90% of them, more often than the 72% typical of monitored counties, and Moderate on 9%. The median day sat at AQI 16; one day in ten went above 50.
The pollutant setting the AQI on an ordinary day here:
- fine particles (PM2.5)100%657 days
Year by year
| Year | Days monitored | Good | Moderate | Over 100 | Over 150 | Median AQI | Highest AQI |
|---|---|---|---|---|---|---|---|
| 2025* | 300 | 271 | 26 | 3 | 2 | 18 | 165 |
| 2024 | 357 | 321 | 33 | 3 | 0 | 14 | 120 |
*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.