Bad Air Days in Pima County, Arizona: 9 a Year
9 bad air days a year
Among the worst tenth of monitored US counties. Ranked 93 of 996 monitored counties, where 1 is worst.
What makes them bad: a mix of particles and ozone (51% 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 July and August 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.
- 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 Pima
In 2000 to 2009 this county averaged 14 bad days a year; in 2016 to 2025, 9. The air has improved. The worst recent year was 2021, with 14 bad days on 365 monitored days.
| Date | AQI | Main pollutant |
|---|---|---|
| 2025-07-01 | 357 | PM10 |
| 2021-06-28 | 313 | PM10 |
| 2020-11-07 | 277 | PM10 |
| 2025-01-08 | 251 | PM10 |
| 2025-06-30 | 189 | PM10 |
An ordinary day in Pima
Across 3,653 monitored days from 2016 to 2025, the air in Pima County rated Good on 38% of them, less often than the 72% typical of monitored counties, and Moderate on 59%. The median day sat at AQI 53; one day in ten went above 80.
The pollutant setting the AQI on an ordinary day here:
- ozone54%1,974 days
- fine particles (PM2.5)25%921 days
- coarse dust (PM10)21%758 days
Every recent year on file
| Year | Days monitored | Good | Moderate | Over 100 | Over 150 | Median AQI | Highest AQI |
|---|---|---|---|---|---|---|---|
| 2025* | 365 | 123 | 234 | 8 | 5 | 54 | 357 |
| 2024 | 366 | 113 | 241 | 12 | 2 | 56 | 171 |
| 2023 | 365 | 123 | 235 | 7 | 0 | 54 | 147 |
| 2022 | 365 | 147 | 205 | 13 | 0 | 53 | 142 |
| 2021 | 365 | 93 | 258 | 14 | 1 | 56 | 313 |
| 2020 | 366 | 124 | 229 | 13 | 1 | 55 | 277 |
| 2019 | 365 | 207 | 156 | 2 | 0 | 49 | 103 |
| 2018 | 365 | 164 | 190 | 11 | 0 | 52 | 129 |
| 2017 | 365 | 121 | 237 | 7 | 0 | 54 | 122 |
| 2016 | 366 | 191 | 171 | 4 | 0 | 50 | 119 |
| 2015 | 365 | 236 | 128 | 1 | 0 | 46 | 101 |
| 2014 | 365 | 197 | 165 | 3 | 0 | 50 | 129 |
| 2013 | 365 | 187 | 170 | 8 | 3 | 50 | 311 |
| 2012 | 366 | 164 | 193 | 9 | 0 | 51 | 143 |
| 2011 | 365 | 166 | 179 | 20 | 0 | 51 | 144 |
| 2010 | 365 | 204 | 156 | 5 | 0 | 49 | 141 |
*2025 may be a partial year in EPA's file.
Nearby counties on file
- Maricopa County89/yr
- Pinal County53/yr
- Gila County14/yr
- Yuma County9/yr
- Santa Cruz County3/yr
- Cochise County3/yr
- La Paz County2/yr
- Coconino County2/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.