SmogRank / United States / California / Stockton
Stockton, month by month
Stockton has a measured daily mean on 1,250 days since 4 January 2023. Its worst month was December 2023, at 73 US AQI (20.8 µg/m³), 149th of 2,247 cities on that month's world ranking. Its cleanest was May 2026, at 27 US AQI (4.9 µg/m³). 2025 averaged 48 US AQI (8.7 µg/m³), against 52 US AQI (9.7 µg/m³) in 2024.
Every month since 2023
The US EPA's Air Quality Index for PM2.5 (2024 breakpoints). Show values as: µg/m³ · US AQI · India AQI · China AQI · European AQI · UK DAQI · Canada AQHI+. About the scales
Months without a mean, and why
4 months
| Month | Why |
|---|---|
| Oct 2026 | 6 of 11 days measured; a month needs 8. The others: 4 with no readings from the monitor, 1 with readings for part of the day (a day needs 18 hours). |
| Nov 2025 | 16 of 30 days measured; a month needs 21. The others: 14 with under 18 hours of readings or readings that failed our checks. |
| Dec 2024 | 19 of 31 days measured; a month needs 22. The others: 12 with under 18 hours of readings or readings that failed our checks. |
| May 2023 | 20 of 31 days measured; a month needs 22. The others: 11 with under 18 hours of readings or readings that failed our checks. |
A day counts once 18 hours of it are measured; a month needs 70% of its days.
Stockton's worst months
| Month | US AQI | World rank | Episode |
|---|---|---|---|
| December 2023 | 7320.8 µg/m³ | 149thof 2,247 | Western United States and Mexico, December 2023 California and Oregon, United States, December 2023 |
| January 2025 | 6516.7 µg/m³ | 410thof 2,474 | California, United States, January 2025 South-western United States and Mexico, December 2024 to January 2025 |
| January 2026 | 6516.6 µg/m³ | 652ndof 2,617 | California, United States, 30 January to 6 February 2026 California and Oregon, United States, January 2026 |
| November 2023 | 6416.1 µg/m³ | 127thof 2,243 | – |
| November 2024 | 6013.9 µg/m³ | 464thof 2,624 | California, United States, November 2024 |
| February 2023 | 5812.6 µg/m³ | 504thof 1,129 | – |
Monthly means over the days measured; finished months only. World rank: its place on that month's world ranking of every city with enough days. Each month opens that ranking.
Stockton's worst days
| Day | US AQI | Episode |
|---|---|---|
| 2 Feb 2023 | 11440.6 µg/m³ | – |
| 25 Dec 2023 | 11239.8 µg/m³ | Western United States and Mexico, December 2023 |
| 17 Dec 2023 | 11139.6 µg/m³ | California and Oregon, United States, December 2023 |
| 4 Dec 2024 | 11039.0 µg/m³ | California and Oregon, United States, December 2024 |
| 20 Sept 2023 | 10537.1 µg/m³ | California and Oregon, United States, September 2023 |
| 26 Dec 2023 | 10537.0 µg/m³ | Western United States and Mexico, December 2023 |
| 15 Dec 2023 | 10436.8 µg/m³ | California and Oregon, United States, December 2023 |
| 5 Dec 2024 | 10436.7 µg/m³ | California and Oregon, United States, December 2024 |
| 29 Nov 2024 | 10336.5 µg/m³ | – |
| 3 Dec 2024 | 10336.2 µg/m³ | California and Oregon, United States, December 2024 |
Daily means, the highest since 4 Jan 2023; the WHO's daily guideline is 15 µg/m³. Each date opens that day's world ranking, and each episode the bad-air spell it was part of.
Use this history
SmogRank, PM2.5 monthly and daily means, Stockton, United States, 4 Jan 2023 – 11 Oct 2026. Monitor data from AirNow, via OpenAQ and from the publisher directly; sources listed at smogrank.com/sources. smogrank.com/us/stockton/history (accessed 12 Oct 2026).
You're welcome to reuse a single chart, image or figure with this citation and a link. Terms. Raw monitor readings in bulk are published by OpenAQ, under each provider's licence.
Stockton now: the last 24 hours, its ranks today and the last 12 months day by day.
Updated 2026-10-12 21:07 UTC. Values are PM2.5 (fine particles), the median of each city's monitors, as the US AQI PM2.5 sub-index. Some low-cost readings: Sensor.Community, ODbL (data and licence). Some readings: Uzhydromet (Uzbekistan's Hydrometeorological Service); Department of Environment, Nepal; Vietnam's government monitors; Aurassure; Umhverfisstofnun (Environment Agency of Iceland); RMCAB (Secretaría Distrital de Ambiente, Bogotá); Love My Air (City and County of Denver), no reuse terms published (why we use them).