Bad Air Days in Cass County, Minnesota: 4 a Year
4 bad air days a year
About the middle of monitored US counties. Ranked 265 of 996 monitored counties, where 1 is worst.
What makes them bad: mostly particles: smoke and dust (100% particle days).
The bad-air season here
- J
- F
- M
- A
- M
- J
- J
- A
- S
- O
- N
- D
Most bad days here fall in July and August. 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.
- 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 13 bad days on 364 monitored days.
| Date | AQI | Main pollutant |
|---|---|---|
| 2021-07-20 | 275 | PM2.5 |
| 2021-07-29 | 195 | PM2.5 |
| 2021-07-30 | 189 | PM2.5 |
| 2025-07-31 | 177 | PM2.5 |
| 2025-07-12 | 172 | PM2.5 |
An ordinary day in Cass
Across 2,801 monitored days from 2018 to 2025, the air in Cass County rated Good on 78% of them, more often than the 72% typical of monitored counties, and Moderate on 21%. The median day sat at AQI 30; one day in ten went above 55.
The pollutant setting the AQI on an ordinary day here:
- fine particles (PM2.5)100%2,801 days
Year by year
| Year | Days monitored | Good | Moderate | Over 100 | Over 150 | Median AQI | Highest AQI |
|---|---|---|---|---|---|---|---|
| 2025* | 364 | 301 | 50 | 13 | 8 | 28 | 177 |
| 2024 | 362 | 313 | 48 | 1 | 1 | 27 | 164 |
| 2023 | 359 | 260 | 94 | 5 | 0 | 32 | 145 |
| 2022 | 348 | 309 | 39 | 0 | 0 | 32 | 64 |
| 2021 | 352 | 103 | 237 | 12 | 5 | 54 | 275 |
| 2020 | 346 | 316 | 30 | 0 | 0 | 22 | 78 |
| 2019 | 350 | 321 | 28 | 1 | 0 | 18 | 125 |
| 2018 | 320 | 268 | 52 | 0 | 0 | 31 | 100 |
| 2012 | 20 | 17 | 3 | 0 | 0 | 22 | 64 |
| 2011 | 37 | 33 | 4 | 0 | 0 | 22 | 58 |
| 2010 | 27 | 27 | 0 | 0 | 0 | 22 | 50 |
*2025 may be a partial year in EPA's file.
Minnesota compared
- Blue Earth County10/yr
- Saint Louis County5/yr
- Wright County5/yr
- Beltrami County4/yr
- Hennepin County4/yr
- Anoka County4/yr
- Becker County4/yr
- Stearns County3/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.