Stockton Best & Worst AQI Days: Air Quality Guide
The worst air quality day on record for Stockton (Stockton-Lodi, CA area) was September 11, 2020, when the daily AQI reached 215 (Very Unhealthy), 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; 7 of the 10 were driven by fine particulate matter (PM2.5) and 2 by coarse dust (PM10), and 8 of them fell in 2020. The cleanest day was July 9, 2023 at AQI 18 (Good); the 10 best days span 5 different years.
Extra Protection for Stockton Homes
Air quality in Stockton is moderate (AQI 60), 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 Stockton's worst and best air quality days?
Worst: September 11, 2020, AQI 215 (Very Unhealthy, PM2.5). Best: July 9, 2023, AQI 18 (Good). Based on 2,557 EPA-monitored days in the Stockton-Lodi, CA area, 2019–2025.
- ✓10 of the 10 worst days were Unhealthy (AQI 151+) or worse; the 10th-worst was AQI 184 (Unhealthy).
- ✓Fine particulate matter (PM2.5) drove 7 of the 10 worst days.
- ✓2020 accounts for 8 of the 10 worst days.
Frequently asked questions
What was the worst air quality day in Stockton?▾
September 11, 2020: the Stockton-Lodi, CA area's daily AQI hit 215 (Very Unhealthy), 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 Stockton?▾
July 9, 2023, with a daily AQI of 18 (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 Stockton's worst air quality day in 2025?▾
January 1, 2025, AQI 93 (Moderate), set by fine particulate matter (PM2.5).
Which pollutant causes Stockton's worst air days?▾
Fine particulate matter (PM2.5) set the AQI on 7 of the 10 worst days; coarse dust (PM10) on 2. The tables above list the defining pollutant for every day.
Stockton's 10 worst air quality days, 2019–2025
Highest daily AQI recorded for the Stockton-Lodi, 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 | (2020 page) | 215 | Very Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
| 2 | (2022 page) | 208 | Very Unhealthy | O3 — ground-level ozone |
| 3 | (2020 page) | 206 | Very Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
| 4 | (2020 page) | 194 | Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
| 5 | (2020 page) | 191 | Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
| 6 | (2020 page) | 191 | Unhealthy | PM10 — coarse dust (PM10) |
| 7 | (2019 page) | 190 | Unhealthy | PM10 — coarse dust (PM10) |
| 8 | (2020 page) | 188 | Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
| 9 | (2020 page) | 186 | Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
| 10 | (2020 page) | 184 | Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
Worst day of each year in Stockton
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 | 190 | Unhealthy | PM10 — coarse dust (PM10) | |
| 2020 | 215 | Very Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season | |
| 2021 | 153 | Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season | |
| 2022 | 208 | Very Unhealthy | O3 — ground-level ozone | |
| 2023 | 119 | Unhealthy for Sensitive Groups | PM10 — coarse dust (PM10) | |
| 2024 | 140 | Unhealthy for Sensitive Groups | O3 — ground-level ozone | |
| 2025 | 93 | Moderate | PM2.5 — fine particulate matter (PM2.5) |
Stockton's 10 best air quality days, 2019–2025
Lowest daily AQI recorded for the Stockton-Lodi, CA area. Ties are listed most recent first.
| # | Date | AQI | Category | Defining pollutant |
|---|---|---|---|---|
| 1 | (2023 page) | 18 | Good | PM2.5 — fine particulate matter (PM2.5) |
| 2 | (2024 page) | 22 | Good | PM2.5 — fine particulate matter (PM2.5) |
| 3 | (2025 page) | 23 | Good | O3 — ground-level ozone, in peak ozone season |
| 4 | (2022 page) | 23 | Good | O3 — ground-level ozone, in peak ozone season |
| 5 | (2021 page) | 23 | Good | PM2.5 — fine particulate matter (PM2.5) |
| 6 | (2025 page) | 24 | Good | PM2.5 — fine particulate matter (PM2.5) |
| 7 | (2025 page) | 24 | Good | PM2.5 — fine particulate matter (PM2.5) |
| 8 | (2022 page) | 24 | Good | O3 — ground-level ozone, in peak ozone season |
| 9 | (2023 page) | 25 | Good | O3 — ground-level ozone |
| 10 | (2022 page) | 25 | Good | O3 — ground-level ozone, in peak ozone season |
Right now in Stockton
The latest EPA AirNow observation puts Stockton's AQI at 60 (PM10). The days above are historical records, not today's reading.
View current Stockton air quality →Source: EPA Air Quality System (AQS) pre-generated Daily AQI by CBSA files — daily AQI by CBSA (Stockton-Lodi, 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.