Visalia Best & Worst AQI Days: Air Quality Guide
The worst air quality day on record for Visalia (Visalia-Porterville, CA area) was September 14, 2021, when the daily AQI reached 961 (Hazardous), set by fine particulate matter (PM2.5), in wildfire smoke season. Across 2,557 monitored days in 2019–2025, 10 of the 10 worst days were Unhealthy (AQI 151+) or worse; 8 of the 10 were driven by fine particulate matter (PM2.5) and 1 by ground-level ozone, and 3 of them fell in 2020. The cleanest day was December 21, 2021 at AQI 21 (Good); the 10 best days span 3 different years.
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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When were Visalia's worst and best air quality days?
Worst: September 14, 2021, AQI 961 (Hazardous, PM2.5). Best: December 21, 2021, AQI 21 (Good). Based on 2,557 EPA-monitored days in the Visalia-Porterville, CA area, 2019–2025.
- ✓10 of the 10 worst days were Unhealthy (AQI 151+) or worse; the 10th-worst was AQI 192 (Unhealthy).
- ✓Fine particulate matter (PM2.5) drove 8 of the 10 worst days.
- ✓2020 accounts for 3 of the 10 worst days.
Frequently asked questions
What was the worst air quality day in Visalia?▾
September 14, 2021: the Visalia-Porterville, CA area's daily AQI hit 961 (Hazardous), driven by fine particulate matter (PM2.5), in wildfire smoke season. That is the highest of 2,557 monitored days in 2019–2025.
What was the best air quality day in Visalia?▾
December 21, 2021, with a daily AQI of 21 (Good). The daily AQI is the highest reading from any monitor in the area, so even the cleanest day reflects the area's worst monitor.
What was Visalia's worst air quality day in 2025?▾
June 18, 2025, AQI 147 (Unhealthy for Sensitive Groups), set by ground-level ozone, in peak ozone season.
Which pollutant causes Visalia's worst air days?▾
Fine particulate matter (PM2.5) set the AQI on 8 of the 10 worst days; ground-level ozone on 1. The tables above list the defining pollutant for every day.
Visalia's 10 worst air quality days, 2019–2025
Highest daily AQI recorded for the Visalia-Porterville, CA area (EPA AQS). The daily AQI is the highest reading from any monitor in the area that day.
| # | Date | AQI | Category | Defining pollutant |
|---|---|---|---|---|
| 1 | (2021 page) | 961 | Hazardous | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
| 2 | (2019 page) | 280 | Very Unhealthy | PM10 — coarse dust (PM10) |
| 3 | (2021 page) | 271 | Very Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
| 4 | (2023 page) | 242 | Very Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
| 5 | (2023 page) | 228 | Very Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
| 6 | (2020 page) | 225 | Very Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
| 7 | (2020 page) | 209 | Very Unhealthy | O3 — ground-level ozone, in peak ozone season |
| 8 | (2021 page) | 205 | Very Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
| 9 | (2023 page) | 198 | Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
| 10 | (2020 page) | 192 | Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
Worst day of each year in Visalia
The single highest-AQI day in each year on record. Click a year for its full month-by-month statistics.
| Year | Worst day | AQI | Category | Defining pollutant |
|---|---|---|---|---|
| 2019 | 280 | Very Unhealthy | PM10 — coarse dust (PM10) | |
| 2020 | 225 | Very Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season | |
| 2021 | 961 | Hazardous | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season | |
| 2022 | 182 | Unhealthy | O3 — ground-level ozone | |
| 2023 | 242 | Very Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season | |
| 2024 | 185 | Unhealthy | O3 — ground-level ozone, in peak ozone season | |
| 2025 | 147 | Unhealthy for Sensitive Groups | O3 — ground-level ozone, in peak ozone season |
Visalia's 10 best air quality days, 2019–2025
Lowest daily AQI recorded for the Visalia-Porterville, CA area. Ties are listed most recent first.
| # | Date | AQI | Category | Defining pollutant |
|---|---|---|---|---|
| 1 | (2021 page) | 21 | Good | O3 — ground-level ozone |
| 2 | (2023 page) | 24 | Good | PM2.5 — fine particulate matter (PM2.5) |
| 3 | (2023 page) | 24 | Good | O3 — ground-level ozone |
| 4 | (2021 page) | 25 | Good | PM2.5 — fine particulate matter (PM2.5) |
| 5 | (2023 page) | 26 | Good | PM2.5 — fine particulate matter (PM2.5) |
| 6 | (2021 page) | 26 | Good | O3 — ground-level ozone |
| 7 | (2021 page) | 26 | Good | O3 — ground-level ozone |
| 8 | (2022 page) | 28 | Good | O3 — ground-level ozone |
| 9 | (2022 page) | 28 | Good | O3 — ground-level ozone |
| 10 | (2021 page) | 28 | Good | O3 — ground-level ozone |
Right now in Visalia
The latest EPA AirNow observation puts Visalia's AQI at 83 (PM10). The days above are historical records, 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.