Bad Air Days in Clermont County, Ohio: 3 a Year
3 bad air days a year
About the middle of monitored US counties. Ranked 429 of 996 monitored counties, where 1 is worst.
What makes them bad: mostly ozone: summer smog (12% particle days).
When the bad days come in Clermont
- J
- F
- M
- A
- M
- J
- J
- A
- S
- O
- N
- D
Most bad days here fall in June and September and July and August. Averaged over 2016 to 2025.
What to buy, and what not to
- 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 worst days on file
In 2000 to 2009 this county averaged 30 bad days a year; in 2016 to 2025, 3. The air has improved. The worst recent year was 2023, with 5 bad days on 358 monitored days.
| Date | AQI | Main pollutant |
|---|---|---|
| 2023-06-28 | 175 | PM2.5 |
| 2019-07-13 | 140 | Ozone |
| 2016-06-11 | 133 | Ozone |
| 2023-06-27 | 133 | PM2.5 |
| 2017-06-03 | 129 | Ozone |
The air on a normal day
Across 3,612 monitored days from 2016 to 2025, the air in Clermont County rated Good on 70% of them, close to the 72% typical of monitored counties, and Moderate on 29%. The median day sat at AQI 43; one day in ten went above 61.
The pollutant setting the AQI on an ordinary day here:
- fine particles (PM2.5)54%1,953 days
- ozone46%1,659 days
Every recent year on file
| Year | Days monitored | Good | Moderate | Over 100 | Over 150 | Median AQI | Highest AQI |
|---|---|---|---|---|---|---|---|
| 2025* | 364 | 280 | 81 | 3 | 0 | 41 | 119 |
| 2024 | 360 | 305 | 52 | 3 | 0 | 39 | 119 |
| 2023 | 358 | 279 | 74 | 5 | 1 | 41 | 175 |
| 2022 | 360 | 238 | 121 | 1 | 0 | 44 | 129 |
| 2021 | 364 | 263 | 101 | 0 | 0 | 42 | 97 |
| 2020 | 361 | 296 | 65 | 0 | 0 | 39 | 100 |
| 2019 | 358 | 247 | 107 | 4 | 0 | 44 | 140 |
| 2018 | 356 | 245 | 109 | 2 | 0 | 44 | 101 |
| 2017 | 365 | 207 | 156 | 2 | 0 | 48 | 129 |
| 2016 | 366 | 164 | 197 | 5 | 0 | 52 | 133 |
| 2015 | 357 | 163 | 191 | 3 | 0 | 52 | 136 |
| 2014 | 353 | 121 | 232 | 0 | 0 | 55 | 100 |
| 2013 | 344 | 144 | 199 | 1 | 0 | 53 | 126 |
| 2012 | 366 | 127 | 216 | 23 | 6 | 54 | 202 |
| 2011 | 365 | 122 | 226 | 17 | 2 | 56 | 179 |
| 2010 | 365 | 87 | 263 | 15 | 1 | 58 | 154 |
*2025 may be a partial year in EPA's file.
Ohio compared
- Hamilton County9/yr
- Cuyahoga County7/yr
- Lucas County7/yr
- Lake County7/yr
- Butler County6/yr
- Warren County5/yr
- Geauga County5/yr
- Ashtabula County4/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.