Bad Air Days in Clay County, Missouri: 6 a Year
6 bad air days a year
More bad air days than three quarters of monitored counties. Ranked 189 of 996 monitored counties, where 1 is worst.
What makes them bad: mostly ozone: summer smog (9% 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 July and September. Averaged over 2016 to 2025.
What to buy, and what not to
- 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, 6. The air has improved. The worst recent year was 2023, with 17 bad days on 350 monitored days.
| Date | AQI | Main pollutant |
|---|---|---|
| 2025-07-09 | 156 | Ozone |
| 2023-09-07 | 153 | PM2.5 |
| 2018-06-06 | 147 | Ozone |
| 2023-06-15 | 140 | Ozone |
| 2025-09-10 | 136 | Ozone |
An ordinary day in Clay
Across 3,611 monitored days from 2016 to 2025, the air in Clay County rated Good on 74% of them, close to the 72% typical of monitored counties, and Moderate on 25%. The median day sat at AQI 42; one day in ten went above 65.
The pollutant setting the AQI on an ordinary day here:
- ozone56%2,037 days
- fine particles (PM2.5)44%1,574 days
Every recent year on file
| Year | Days monitored | Good | Moderate | Over 100 | Over 150 | Median AQI | Highest AQI |
|---|---|---|---|---|---|---|---|
| 2025* | 363 | 270 | 86 | 7 | 1 | 42 | 156 |
| 2024 | 366 | 286 | 76 | 4 | 0 | 41 | 122 |
| 2023 | 350 | 228 | 105 | 17 | 1 | 43 | 153 |
| 2022 | 365 | 286 | 75 | 4 | 0 | 41 | 112 |
| 2021 | 350 | 270 | 76 | 4 | 0 | 41 | 129 |
| 2020 | 364 | 287 | 76 | 1 | 0 | 39 | 101 |
| 2019 | 365 | 266 | 99 | 0 | 0 | 43 | 90 |
| 2018 | 363 | 251 | 101 | 11 | 0 | 42 | 147 |
| 2017 | 364 | 248 | 112 | 4 | 0 | 43 | 129 |
| 2016 | 361 | 273 | 85 | 3 | 0 | 41 | 119 |
| 2015 | 362 | 217 | 141 | 4 | 0 | 46 | 115 |
| 2014 | 365 | 204 | 157 | 4 | 0 | 46 | 120 |
| 2013 | 364 | 197 | 160 | 7 | 0 | 49 | 136 |
| 2012 | 364 | 163 | 169 | 32 | 6 | 52 | 177 |
| 2011 | 365 | 174 | 169 | 22 | 3 | 52 | 172 |
| 2010 | 365 | 174 | 178 | 13 | 0 | 52 | 129 |
*2025 may be a partial year in EPA's file.
Nearby counties on file
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.