Bad Air Days in Lake County, Montana
Not enough data
EPA monitors in Lake County ran on too few days between 2016 and 2025 to give a fair yearly count (about 30% of days covered). Neighbouring counties below are a better guide.
Is a purifier worth it here?
- EPA monitors here ran too few days to give a fair yearly count. Use AirNow for today's air.
The worst days on file
The worst recent year was 2020, with 3 bad days on 117 monitored days.
| Date | AQI | Main pollutant |
|---|---|---|
| 2017-09-07 | 195 | PM2.5 |
| 2020-09-15 | 183 | PM2.5 |
| 2023-08-19 | 157 | PM2.5 |
| 2020-09-18 | 154 | PM2.5 |
| 2021-08-14 | 152 | PM2.5 |
The air on a normal day
Across 1,091 monitored days from 2016 to 2025, the air in Lake County rated Good on 94% of them, more often than the 72% typical of monitored counties, and Moderate on 5%. The median day sat at AQI 10; one day in ten went above 39.
The pollutant setting the AQI on an ordinary day here:
- fine particles (PM2.5)100%1,091 days
Year by year
| Year | Days monitored | Good | Moderate | Over 100 | Over 150 | Median AQI | Highest AQI |
|---|---|---|---|---|---|---|---|
| 2025* | 95 | 92 | 3 | 0 | 0 | 11 | 79 |
| 2024 | 115 | 108 | 7 | 0 | 0 | 9 | 77 |
| 2023 | 109 | 101 | 6 | 2 | 1 | 13 | 157 |
| 2022 | 97 | 93 | 3 | 1 | 0 | 11 | 120 |
| 2021 | 117 | 105 | 9 | 3 | 1 | 9 | 152 |
| 2020 | 117 | 111 | 3 | 3 | 2 | 7 | 183 |
| 2019 | 93 | 92 | 1 | 0 | 0 | 10 | 53 |
| 2018 | 118 | 107 | 8 | 3 | 0 | 11 | 117 |
| 2017 | 110 | 99 | 9 | 2 | 1 | 9 | 195 |
| 2016 | 120 | 117 | 2 | 1 | 0 | 8 | 130 |
| 2015 | 120 | 110 | 8 | 2 | 1 | 12 | 172 |
| 2014 | 117 | 111 | 6 | 0 | 0 | 11 | 90 |
| 2013 | 120 | 116 | 4 | 0 | 0 | 11 | 56 |
| 2012 | 120 | 112 | 8 | 0 | 0 | 9 | 87 |
| 2011 | 226 | 221 | 4 | 1 | 0 | 11 | 102 |
| 2010 | 359 | 352 | 7 | 0 | 0 | 13 | 62 |
*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.