Bad Air Days in Mono County, California: 23 a Year
23 bad air days a year
Among the worst tenth of monitored US counties. Ranked 27 of 996 monitored counties, where 1 is worst.
What makes them bad: mostly particles: smoke and dust (100% 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 September and October and August. Averaged over 2016 to 2025.
Is a purifier worth it here?
- 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.
- With this many bad days, whole-home filtration is worth an HVAC contractor quote.
The worst days on file
In 2000 to 2009 this county averaged 19 bad days a year; in 2016 to 2025, 23. It has got worse. The worst recent year was 2020, with 66 bad days on 366 monitored days.
| Date | AQI | Main pollutant |
|---|---|---|
| 2022-06-12 | 8368 | PM10 |
| 2022-05-06 | 7835 | PM10 |
| 2016-10-15 | 7063 | PM10 |
| 2016-05-19 | 4335 | PM10 |
| 2019-05-15 | 4227 | PM10 |
An ordinary day in Mono
Across 3,652 monitored days from 2016 to 2025, the air in Mono County rated Good on 77% of them, more often than the 72% typical of monitored counties, and Moderate on 16%. The median day sat at AQI 27; one day in ten went above 82.
The pollutant setting the AQI on an ordinary day here:
- fine particles (PM2.5)58%2,100 days
- coarse dust (PM10)42%1,552 days
Year by year
| Year | Days monitored | Good | Moderate | Over 100 | Over 150 | Median AQI | Highest AQI |
|---|---|---|---|---|---|---|---|
| 2025* | 365 | 329 | 29 | 7 | 4 | 21 | 704 |
| 2024 | 366 | 341 | 25 | 0 | 0 | 19 | 69 |
| 2023 | 365 | 325 | 35 | 5 | 4 | 24 | 1829 |
| 2022 | 365 | 276 | 61 | 28 | 23 | 27 | 8368 |
| 2021 | 364 | 260 | 78 | 26 | 14 | 27 | 2971 |
| 2020 | 366 | 183 | 117 | 66 | 53 | 51 | 2088 |
| 2019 | 365 | 242 | 108 | 15 | 9 | 34 | 4227 |
| 2018 | 365 | 252 | 84 | 29 | 15 | 27 | 1049 |
| 2017 | 365 | 300 | 40 | 25 | 20 | 18 | 3767 |
| 2016 | 366 | 312 | 21 | 33 | 30 | 18 | 7063 |
| 2015 | 365 | 318 | 28 | 19 | 17 | 15 | 4384 |
| 2014 | 365 | 332 | 21 | 12 | 11 | 16 | 2739 |
| 2013 | 365 | 311 | 43 | 11 | 5 | 19 | 3479 |
| 2012 | 366 | 326 | 16 | 24 | 19 | 18 | 4244 |
| 2011 | 365 | 313 | 34 | 18 | 14 | 18 | 5260 |
| 2010 | 365 | 308 | 35 | 22 | 18 | 18 | 4658 |
*2025 may be a partial year in EPA's file.
Elsewhere in California
- San Bernardino County138/yr
- Riverside County132/yr
- Kern County109/yr
- Tulare County107/yr
- Los Angeles County106/yr
- Fresno County81/yr
- Kings County49/yr
- Imperial County40/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.