Visalia Air Quality in December
Across 2019–2025, Visalia's December air quality had a median AQI of 66 (Moderate) over 217 monitored days in the Visalia-Porterville, CA area. 14.3% of December days (31 of 217) reached Unhealthy for Sensitive Groups or worse, and fine particulate matter (PM2.5) set the daily AQI on 86.2% of days. The cleanest December on record here was 2019 (median AQI 56, 0 days above 100) and the worst was 2020 (median 82, 10 days above 100, peak AQI 129).
- Good: 21.7%
- Moderate: 64.1%
- Unhealthy for Sensitive Groups: 11.1%
- Unhealthy or worse: 3.2%
Extra Protection for Visalia Homes
Air quality in Visalia is moderate (AQI 66), with fine particles (PM2.5) 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.
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How is the air in Visalia in December?
Moderate on a typical day: median AQI 66 across 2019–2025, with 14.3% of December days above AQI 100. Fine particulate matter (PM2.5) is the main driver.
- ✓21.7% of December days were Good (AQI 0–50), 64.1% Moderate (51–100).
- ✓31 days of 217 reached AQI 101+; the December peak was 157.
- ✓Best December: 2019; worst December: 2020.
Frequently asked questions
What is the air quality like in Visalia in December?▾
Across 2019–2025, the median daily AQI in Visalia in December was 66 (Moderate). 21.7% of days were Good, 64.1% Moderate, and 14.3% reached Unhealthy for Sensitive Groups or worse, based on 217 monitored days in EPA's Air Quality System.
Is December a good time for outdoor exercise in Visalia?▾
A typical December day in Visalia is Moderate (median AQI 66): outdoor exercise is acceptable for most people, but unusually sensitive individuals should watch for symptoms, and about 1 day in 7 of December days (14.3%) reached AQI 101+ — the level at which EPA advises people with asthma, children and older adults to shorten hard outdoor exertion.
Which pollutant causes Visalia's December air quality problems?▾
Fine particulate matter (PM2.5) set the daily AQI on 86.2% of December days in Visalia. The highest December AQI recorded in 2019–2025 was 157 (Unhealthy), in 2020.
Visalia December air quality, year by year
Visalia December air quality by year (Visalia-Porterville, CA, EPA AQS daily AQI)
| Year | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| 2019cleanest | 31 | 56 | 0 | 96 | PM2.5 |
| 2020worst | 31 | 82 | 10 | 129 | PM2.5 |
| 2021 | 31 | 36 | 4 | 157 | PM2.5 |
| 2022 | 31 | 67 | 2 | 108 | PM2.5 |
| 2023 | 31 | 74 | 7 | 119 | PM2.5 |
| 2024 | 31 | 75 | 8 | 157 | PM2.5 |
| 2025 | 31 | 63 | 0 | 99 | PM2.5 |
What December air means in Visalia
A typical December day in Visalia is Moderate (median AQI 66): outdoor exercise is acceptable for most people, but unusually sensitive individuals should watch for symptoms, and about 1 day in 7 of December days (14.3%) reached AQI 101+ — the level at which EPA advises people with asthma, children and older adults to shorten hard outdoor exertion.
December's median AQI of 66 is below Visalia's whole-year median of 71, making it one of the area's cleaner periods. Nationally, the median December AQI across every EPA metro area (95,590 metro-days, 2019–2025) is 39, so Visalia runs above the national December norm; 14.3% of its December days topped AQI 100 versus 0.7% nationally (above average).
December is part of Visalia's winter season (December, January, February); the winter 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 66 (PM2.5). 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.