Bad Air Days in Allegan County, Michigan: 9 a Year
9 bad air days a year
More bad air days than three quarters of monitored counties. Ranked 105 of 996 monitored counties, where 1 is worst.
What makes them bad: mostly ozone: summer smog (8% particle days).
When the bad days come in Allegan
- J
- F
- M
- A
- M
- J
- J
- A
- S
- O
- N
- D
Most bad days here fall in June and July. Averaged over 2016 to 2025.
Is a purifier worth it here?
- Ozone drives many bad days here. Purifiers and filters do not remove ozone, so do not buy one for that. Ozone peaks on hot afternoons: exercise outside in the morning.
Better or worse than it was
In 2000 to 2009 this county averaged 27 bad days a year; in 2016 to 2025, 9. The air has improved. The worst recent year was 2025, with 14 bad days on 363 monitored days.
| Date | AQI | Main pollutant |
|---|---|---|
| 2022-06-21 | 195 | Ozone |
| 2022-06-20 | 174 | Ozone |
| 2023-07-25 | 161 | Ozone |
| 2025-06-11 | 151 | Ozone |
| 2025-07-31 | 151 | PM2.5 |
The air on a normal day
Across 3,221 monitored days from 2016 to 2025, the air in Allegan County rated Good on 71% of them, close to the 72% typical of monitored counties, and Moderate on 26%. The median day sat at AQI 41; one day in ten went above 67.
The pollutant setting the AQI on an ordinary day here:
- ozone59%1,914 days
- fine particles (PM2.5)41%1,307 days
Every recent year on file
| Year | Days monitored | Good | Moderate | Over 100 | Over 150 | Median AQI | Highest AQI |
|---|---|---|---|---|---|---|---|
| 2025* | 363 | 232 | 117 | 14 | 2 | 44 | 151 |
| 2024 | 351 | 222 | 125 | 4 | 0 | 46 | 115 |
| 2023 | 360 | 246 | 102 | 12 | 1 | 42 | 161 |
| 2022 | 344 | 256 | 82 | 6 | 2 | 40 | 195 |
| 2021 | 361 | 245 | 107 | 9 | 0 | 42 | 136 |
| 2020 | 359 | 275 | 78 | 6 | 0 | 37 | 136 |
| 2019 | 276 | 224 | 48 | 4 | 0 | 39 | 115 |
| 2018 | 286 | 218 | 60 | 8 | 0 | 40 | 150 |
| 2017 | 281 | 207 | 70 | 4 | 0 | 41 | 115 |
| 2016 | 240 | 174 | 57 | 9 | 0 | 43 | 150 |
| 2015 | 243 | 169 | 70 | 4 | 0 | 42 | 147 |
| 2014 | 240 | 164 | 69 | 7 | 1 | 44 | 151 |
| 2013 | 240 | 150 | 82 | 8 | 1 | 44 | 154 |
| 2012 | 240 | 139 | 65 | 36 | 11 | 47 | 195 |
| 2011 | 242 | 163 | 70 | 9 | 3 | 40 | 179 |
| 2010 | 244 | 156 | 83 | 5 | 0 | 44 | 122 |
*2025 may be a partial year in EPA's file.
Elsewhere in Michigan
- Wayne County11/yr
- Marquette County9/yr
- Muskegon County9/yr
- Berrien County8/yr
- Macomb County7/yr
- Cass County6/yr
- Oakland County6/yr
- St. Clair County5/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, and on why a purifier does not touch ozone in smoke vs ozone.