Visalia Air Quality in September
Across 2019–2025, Visalia's September air quality had a median AQI of 107 (Unhealthy for Sensitive Groups) over 210 monitored days in the Visalia-Porterville, CA area. 55.7% of September days (117 of 210) reached Unhealthy for Sensitive Groups or worse, and ground-level ozone set the daily AQI on 65.7% of days. The cleanest September on record here was 2025 (median AQI 74, 6 days above 100) and the worst was 2020 (median 143, 24 days above 100, peak AQI 192).
- Good: 10.0%
- Moderate: 34.3%
- Unhealthy for Sensitive Groups: 37.6%
- Unhealthy or worse: 18.1%
Extra Protection for Visalia Homes
Air quality in Visalia is moderate (AQI 83), 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 Visalia in September?
Unhealthy for Sensitive Groups on a typical day: median AQI 107 across 2019–2025, with 55.7% of September days above AQI 100. Ground-level ozone is the main driver.
- ✓10.0% of September days were Good (AQI 0–50), 34.3% Moderate (51–100).
- ✓117 days of 210 reached AQI 101+; the September peak was 961.
- ✓Best September: 2025; worst September: 2020.
Frequently asked questions
What is the air quality like in Visalia in September?▾
Across 2019–2025, the median daily AQI in Visalia in September was 107 (Unhealthy for Sensitive Groups). 10.0% of days were Good, 34.3% Moderate, and 55.7% 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 Visalia?▾
A typical September day in Visalia is already Unhealthy for Sensitive Groups (median AQI 107): people with asthma or heart disease, children and older adults should reduce prolonged outdoor exertion on most days, and about 56% of September days (55.7%) were at that level or worse.
Which pollutant causes Visalia's September air quality problems?▾
Ground-level ozone set the daily AQI on 65.7% of September days in Visalia. The highest September AQI recorded in 2019–2025 was 961 (Hazardous), in 2020.
Visalia September air quality, year by year
Visalia September air quality by year (Visalia-Porterville, CA, EPA AQS daily AQI)
| Year | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| 2019 | 30 | 92 | 13 | 136 | O3 |
| 2020worst | 30 | 143 | 24 | 192 | PM2.5 |
| 2021 | 30 | 116 | 21 | 961 | PM2.5 |
| 2022 | 30 | 105 | 17 | 182 | O3 |
| 2023 | 30 | 106 | 17 | 242 | PM2.5 |
| 2024 | 30 | 116 | 19 | 161 | O3 |
| 2025cleanest | 30 | 74 | 6 | 129 | O3 |
What September air means in Visalia
A typical September day in Visalia is already Unhealthy for Sensitive Groups (median AQI 107): people with asthma or heart disease, children and older adults should reduce prolonged outdoor exertion on most days, and about 56% of September days (55.7%) were at that level or worse.
September's median AQI of 107 is above Visalia's whole-year median of 71, 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 Visalia runs above the national September norm; 55.7% of its September days topped AQI 100 versus 2.7% nationally (above average).
September is part of Visalia's fall season (September, October, November); the fall page pools all three months.
Activity-specific thresholds: running, cycling, kids' sports.
Right now in Visalia
The latest EPA AirNow observation puts Visalia's AQI at 83 (PM10). The figures above are multi-year month statistics, not today's reading.
View current Visalia air quality →Source: EPA Air Quality System (AQS) pre-generated Daily AQI by CBSA files — daily AQI by CBSA (Visalia-Porterville, 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.