Phoenix Air Quality in September
Across 2019–2025, Phoenix's September air quality had a median AQI of 85 (Moderate) over 210 monitored days in the Phoenix-Mesa-Scottsdale, AZ area. 35.7% of September days (75 of 210) reached Unhealthy for Sensitive Groups or worse, and ground-level ozone set the daily AQI on 58.1% of days. The cleanest September on record here was 2023 (median AQI 74, 2 days above 100) and the worst was 2021 (median 213, 30 days above 100, peak AQI 239).
- Good: 8.1%
- Moderate: 56.2%
- Unhealthy for Sensitive Groups: 17.6%
- Unhealthy or worse: 18.1%
Reduce Indoor Ozone in Phoenix
Today's main pollutant in Phoenix is ground-level ozone (AQI 47). Important: standard HEPA filters do NOT remove ozone — only a purifier with a substantial activated-carbon bed adsorbs it. The biggest wins are cutting indoor sources (gas appliances, certain "ionizer" purifiers) and ventilating when outdoor ozone is low (early morning). A high-carbon unit helps with the gases and VOCs that linger indoors.
Recommended: Levoit Core 300 — True HEPA + activated carbon · CADR ~141 CFM · rooms up to 219 sq ft
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How is the air in Phoenix in September?
Moderate on a typical day: median AQI 85 across 2019–2025, with 35.7% of September days above AQI 100. Ground-level ozone is the main driver.
- ✓8.1% of September days were Good (AQI 0–50), 56.2% Moderate (51–100).
- ✓75 days of 210 reached AQI 101+; the September peak was 329.
- ✓Best September: 2023; worst September: 2021.
Frequently asked questions
What is the air quality like in Phoenix in September?▾
Across 2019–2025, the median daily AQI in Phoenix in September was 85 (Moderate). 8.1% of days were Good, 56.2% Moderate, and 35.7% reached Unhealthy for Sensitive Groups or worse, based on 210 monitored days in EPA's Air Quality System.
Is September a good time for outdoor exercise in Phoenix?▾
A typical September day in Phoenix is Moderate (median AQI 85): outdoor exercise is acceptable for most people, but unusually sensitive individuals should watch for symptoms, and about 1 day in 3 of September days (35.7%) reached AQI 101+ — the level at which EPA advises people with asthma, children and older adults to shorten hard outdoor exertion.
Which pollutant causes Phoenix's September air quality problems?▾
Ground-level ozone set the daily AQI on 58.1% of September days in Phoenix. The highest September AQI recorded in 2019–2025 was 329 (Hazardous), in 2021.
Phoenix September air quality, year by year
Phoenix September air quality by year (Phoenix-Mesa-Scottsdale, AZ, EPA AQS daily AQI)
| Year | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| 2019 | 30 | 73 | 6 | 151 | O3 |
| 2020 | 30 | 97 | 14 | 164 | PM10 |
| 2021worst | 30 | 213 | 30 | 239 | O3 |
| 2022 | 30 | 72 | 5 | 158 | O3 |
| 2023cleanest | 30 | 74 | 2 | 164 | PM10 |
| 2024 | 30 | 90 | 13 | 152 | PM10 |
| 2025 | 30 | 64 | 5 | 329 | PM10 |
What September air means in Phoenix
A typical September day in Phoenix is Moderate (median AQI 85): outdoor exercise is acceptable for most people, but unusually sensitive individuals should watch for symptoms, and about 1 day in 3 of September days (35.7%) reached AQI 101+ — the level at which EPA advises people with asthma, children and older adults to shorten hard outdoor exertion.
September's median AQI of 85 is above Phoenix's whole-year median of 79, making it one of the area's dirtier periods. Nationally, the median September AQI across every EPA metro area (100,699 metro-days, 2019–2025) is 43, so Phoenix runs above the national September norm; 35.7% of its September days topped AQI 100 versus 2.7% nationally (above average).
September is part of Phoenix's fall season (September, October, November); the fall page pools all three months.
Activity-specific thresholds: running, cycling, kids' sports.
Right now in Phoenix
The latest EPA AirNow observation puts Phoenix's AQI at 47 (O3). The figures above are multi-year month statistics, not today's reading.
View current Phoenix air quality →Source: EPA Air Quality System (AQS) pre-generated Daily AQI by CBSA files — daily AQI by CBSA (Phoenix-Mesa-Scottsdale, AZ), 2019–2025. Daily AQI per CBSA is the highest AQI reported by any monitor in the area that day; the defining parameter is the pollutant that set it. Month and season statistics pool every such day in the period across all years listed. Retrieved 2026-09-09.