Bad Air Days in Imperial County, California: 40 a Year
40 bad air days a year
Among the worst tenth of monitored US counties. Ranked 10 of 996 monitored counties, where 1 is worst.
What makes them bad: a mix of particles and ozone (48% 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 May and June. Averaged over 2016 to 2025.
What to buy, and what not to
- Particles (wildfire smoke, dust) cause enough bad days here to matter. A HEPA purifier sized to your bedroom removes them; run it with windows shut on bad days.
- Upgrade the furnace or AC filter to MERV 13 so the whole house is filtered, not just one room.
- 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.
- Sign up for EnviroFlash ozone alerts for this area during the worst months.
The worst days on file
In 2000 to 2009 this county averaged 57 bad days a year; in 2016 to 2025, 40. The air has improved. The worst recent year was 2018, with 50 bad days on 365 monitored days.
| Date | AQI | Main pollutant |
|---|---|---|
| 2022-02-21 | 791 | PM10 |
| 2022-05-29 | 759 | PM10 |
| 2022-02-15 | 679 | PM10 |
| 2016-12-16 | 546 | PM10 |
| 2023-04-03 | 506 | PM10 |
The air on a normal day
Across 3,653 monitored days from 2016 to 2025, the air in Imperial County rated Good on 23% of them, less often than the 72% typical of monitored counties, and Moderate on 66%. The median day sat at AQI 62; one day in ten went above 103.
The pollutant setting the AQI on an ordinary day here:
- ozone42%1,520 days
- fine particles (PM2.5)35%1,282 days
- coarse dust (PM10)23%837 days
Every recent year on file
| Year | Days monitored | Good | Moderate | Over 100 | Over 150 | Median AQI | Highest AQI |
|---|---|---|---|---|---|---|---|
| 2025* | 365 | 101 | 220 | 44 | 10 | 64 | 426 |
| 2024 | 366 | 83 | 233 | 50 | 8 | 63 | 341 |
| 2023 | 365 | 104 | 214 | 47 | 10 | 61 | 506 |
| 2022 | 365 | 86 | 232 | 47 | 13 | 61 | 791 |
| 2021 | 365 | 84 | 252 | 29 | 7 | 60 | 436 |
| 2020 | 366 | 94 | 244 | 28 | 2 | 60 | 166 |
| 2019 | 365 | 94 | 250 | 21 | 2 | 61 | 185 |
| 2018 | 365 | 67 | 248 | 50 | 9 | 64 | 286 |
| 2017 | 365 | 73 | 250 | 42 | 5 | 64 | 328 |
| 2016 | 366 | 64 | 257 | 45 | 6 | 61 | 546 |
| 2015 | 365 | 49 | 274 | 42 | 3 | 66 | 184 |
| 2014 | 365 | 24 | 287 | 54 | 9 | 69 | 352 |
| 2013 | 365 | 137 | 189 | 39 | 4 | 58 | 207 |
| 2012 | 366 | 160 | 167 | 39 | 5 | 55 | 274 |
| 2011 | 365 | 176 | 156 | 33 | 1 | 52 | 168 |
| 2010 | 365 | 151 | 163 | 51 | 0 | 57 | 140 |
*2025 may be a partial year in EPA's file.
California compared
- San Bernardino County138/yr
- Riverside County132/yr
- Kern County109/yr
- Tulare County107/yr
- Los Angeles County106/yr
- Fresno County81/yr
- Kings County49/yr
- San Diego County38/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.