Bad Air Days in Warren County, Ohio: 5 a Year
5 bad air days a year
More bad air days than three quarters of monitored counties. Ranked 231 of 996 monitored counties, where 1 is worst.
What makes them bad: mostly ozone: summer smog (6% particle days).
When the bad days come in Warren
- J
- F
- M
- A
- M
- J
- J
- A
- S
- O
- N
- D
Most bad days here fall in June and July and August and September. Averaged over 2016 to 2025.
What actually helps 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.
The record for Warren
In 2000 to 2009 this county averaged 43 bad days a year; in 2016 to 2025, 5. The air has improved. The worst recent year was 2016, with 9 bad days on 360 monitored days.
| Date | AQI | Main pollutant |
|---|---|---|
| 2023-06-28 | 183 | PM2.5 |
| 2023-06-27 | 154 | PM2.5 |
| 2024-08-27 | 147 | Ozone |
| 2018-05-25 | 136 | Ozone |
| 2023-06-29 | 134 | PM2.5 |
The air on a normal day
Across 3,606 monitored days from 2016 to 2025, the air in Warren County rated Good on 62% of them, less often than the 72% typical of monitored counties, and Moderate on 37%. The median day sat at AQI 46; one day in ten went above 66.
The pollutant setting the AQI on an ordinary day here:
- fine particles (PM2.5)56%2,033 days
- ozone44%1,573 days
Warren County by year
| Year | Days monitored | Good | Moderate | Over 100 | Over 150 | Median AQI | Highest AQI |
|---|---|---|---|---|---|---|---|
| 2025* | 364 | 247 | 110 | 7 | 0 | 44 | 126 |
| 2024 | 365 | 267 | 92 | 6 | 0 | 43 | 147 |
| 2023 | 364 | 230 | 127 | 7 | 2 | 44 | 183 |
| 2022 | 356 | 231 | 122 | 3 | 0 | 44 | 133 |
| 2021 | 360 | 230 | 128 | 2 | 0 | 44 | 119 |
| 2020 | 361 | 248 | 109 | 4 | 0 | 44 | 115 |
| 2019 | 360 | 210 | 147 | 3 | 0 | 47 | 122 |
| 2018 | 358 | 201 | 152 | 5 | 0 | 48 | 136 |
| 2017 | 358 | 185 | 172 | 1 | 0 | 49 | 115 |
| 2016 | 360 | 186 | 165 | 9 | 0 | 50 | 129 |
| 2015 | 344 | 200 | 140 | 4 | 0 | 47 | 129 |
| 2014 | 342 | 82 | 255 | 5 | 0 | 57 | 112 |
| 2013 | 349 | 30 | 316 | 3 | 0 | 60 | 112 |
| 2012 | 361 | 70 | 280 | 11 | 2 | 58 | 166 |
| 2011 | 350 | 95 | 237 | 18 | 1 | 57 | 166 |
| 2010 | 365 | 84 | 270 | 11 | 0 | 59 | 150 |
*2025 may be a partial year in EPA's file.
Nearby counties on file
- Hamilton County9/yr
- Cuyahoga County7/yr
- Lucas County7/yr
- Lake County7/yr
- Butler County6/yr
- Geauga County5/yr
- Ashtabula County4/yr
- Franklin 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.