Bad Air Days in Peoria County, Illinois: 4 a Year
4 bad air days a year
About the middle of monitored US counties. Ranked 287 of 996 monitored counties, where 1 is worst.
What makes them bad: mostly ozone: summer smog (13% 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 June and May. 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.
The worst days on file
In 2000 to 2009 this county averaged 9 bad days a year; in 2016 to 2025, 4. The air has improved. The worst recent year was 2023, with 22 bad days on 340 monitored days.
| Date | AQI | Main pollutant |
|---|---|---|
| 2025-07-31 | 154 | PM2.5 |
| 2025-08-01 | 154 | PM2.5 |
| 2023-05-24 | 151 | Ozone |
| 2023-06-03 | 143 | Ozone |
| 2023-06-28 | 136 | Ozone |
An ordinary day in Peoria
Across 3,545 monitored days from 2016 to 2025, the air in Peoria County rated Good on 58% of them, less often than the 72% typical of monitored counties, and Moderate on 41%. The median day sat at AQI 47; one day in ten went above 65.
The pollutant setting the AQI on an ordinary day here:
- fine particles (PM2.5)62%2,209 days
- ozone38%1,336 days
Year by year
| Year | Days monitored | Good | Moderate | Over 100 | Over 150 | Median AQI | Highest AQI |
|---|---|---|---|---|---|---|---|
| 2025* | 357 | 214 | 139 | 4 | 2 | 45 | 154 |
| 2024 | 344 | 236 | 108 | 0 | 0 | 44 | 100 |
| 2023 | 340 | 187 | 131 | 22 | 1 | 48 | 151 |
| 2022 | 319 | 181 | 138 | 0 | 0 | 48 | 100 |
| 2021 | 361 | 181 | 179 | 1 | 0 | 50 | 101 |
| 2020 | 364 | 247 | 116 | 1 | 0 | 44 | 115 |
| 2019 | 364 | 236 | 126 | 2 | 0 | 44 | 101 |
| 2018 | 365 | 189 | 173 | 3 | 0 | 49 | 101 |
| 2017 | 365 | 172 | 190 | 3 | 0 | 51 | 115 |
| 2016 | 366 | 206 | 158 | 2 | 0 | 48 | 108 |
| 2015 | 365 | 201 | 164 | 0 | 0 | 47 | 90 |
| 2014 | 365 | 204 | 161 | 0 | 0 | 46 | 100 |
| 2013 | 365 | 166 | 199 | 0 | 0 | 52 | 97 |
| 2012 | 366 | 144 | 201 | 21 | 0 | 54 | 140 |
| 2011 | 365 | 104 | 258 | 3 | 1 | 56 | 159 |
| 2010 | 365 | 114 | 248 | 3 | 0 | 56 | 105 |
*2025 may be a partial year in EPA's file.
Elsewhere in Illinois
- Cook County18/yr
- Lake County9/yr
- Madison County8/yr
- Kane County7/yr
- McHenry County7/yr
- DuPage County5/yr
- Jersey County5/yr
- Winnebago 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.