Fresno Air Quality in September
Across 2019–2025, Fresno's September air quality had a median AQI of 88 (Moderate) over 210 monitored days in the Fresno, CA area. 39.5% of September days (83 of 210) reached Unhealthy for Sensitive Groups or worse, and ground-level ozone set the daily AQI on 66.7% of days. The cleanest September on record here was 2023 (median AQI 74, 6 days above 100) and the worst was 2020 (median 162, 22 days above 100, peak AQI 346).
- Good: 15.2%
- Moderate: 45.2%
- Unhealthy for Sensitive Groups: 30.0%
- Unhealthy or worse: 9.5%
Extra Protection for Fresno Homes
Air quality in Fresno is moderate (AQI 69), with particle pollution the main concern. A True-HEPA purifier gives sensitive groups — kids, seniors and anyone with asthma or allergies — cleaner air indoors on days like today.
Recommended: Coway AP-1512HH Mighty — True HEPA + carbon · CADR ~246 CFM · rooms up to 361 sq ft
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How is the air in Fresno in September?
Moderate on a typical day: median AQI 88 across 2019–2025, with 39.5% of September days above AQI 100. Ground-level ozone is the main driver.
- ✓15.2% of September days were Good (AQI 0–50), 45.2% Moderate (51–100).
- ✓83 days of 210 reached AQI 101+; the September peak was 346.
- ✓Best September: 2023; worst September: 2020.
Frequently asked questions
What is the air quality like in Fresno in September?▾
Across 2019–2025, the median daily AQI in Fresno in September was 88 (Moderate). 15.2% of days were Good, 45.2% Moderate, and 39.5% 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 Fresno?▾
A typical September day in Fresno is Moderate (median AQI 88): outdoor exercise is acceptable for most people, but unusually sensitive individuals should watch for symptoms, and about 1 day in 3 of September days (39.5%) reached AQI 101+ — the level at which EPA advises people with asthma, children and older adults to shorten hard outdoor exertion.
Which pollutant causes Fresno's September air quality problems?▾
Ground-level ozone set the daily AQI on 66.7% of September days in Fresno. The highest September AQI recorded in 2019–2025 was 346 (Hazardous), in 2020.
Fresno September air quality, year by year
Fresno September air quality by year (Fresno, CA, EPA AQS daily AQI)
| Year | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| 2019 | 30 | 77 | 10 | 147 | O3 |
| 2020worst | 30 | 162 | 22 | 346 | PM2.5 |
| 2021 | 30 | 88 | 12 | 167 | O3 |
| 2022 | 30 | 84 | 12 | 150 | O3 |
| 2023cleanest | 30 | 74 | 6 | 140 | O3 |
| 2024 | 30 | 97 | 13 | 143 | O3 |
| 2025 | 30 | 64 | 8 | 147 | O3 |
What September air means in Fresno
A typical September day in Fresno is Moderate (median AQI 88): outdoor exercise is acceptable for most people, but unusually sensitive individuals should watch for symptoms, and about 1 day in 3 of September days (39.5%) 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 88 is above Fresno's whole-year median of 67, 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 Fresno runs above the national September norm; 39.5% of its September days topped AQI 100 versus 2.7% nationally (above average).
September is part of Fresno's fall season (September, October, November); the fall page pools all three months.
Activity-specific thresholds: running, cycling, kids' sports.
Right now in Fresno
The latest EPA AirNow observation puts Fresno's AQI at 69 (PM10). The figures above are multi-year month statistics, not today's reading.
View current Fresno air quality →Source: EPA Air Quality System (AQS) pre-generated Daily AQI by CBSA files — daily AQI by CBSA (Fresno, CA), 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.