SmogRank / United States / California / Oceano
Oceano, month by month
Oceano has a measured daily mean on 1,288 days since 1 January 2023. Its worst month was September 2023, at 56 US AQI (11.8 µg/m³), 347th of 2,176 cities on that month's world ranking. Its cleanest was July 2025, at 19 US AQI (3.5 µg/m³). 2025 averaged 37 US AQI (6.7 µg/m³), against 33 US AQI (5.9 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
2 months
| Month | Why |
|---|---|
| Mar 2023 | 11 of 31 days measured; a month needs 22. The others: 20 missing from OpenAQ's archive. |
| Feb 2023 | 1 of 28 days measured; a month needs 20. The others: 25 missing from OpenAQ's archive, 2 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.
Oceano's worst months
| Month | US AQI | World rank | Episode |
|---|---|---|---|
| September 2023 | 5611.8 µg/m³ | 347thof 2,176 | California and Oregon, United States, September 2023 |
| May 2025 | 5511.4 µg/m³ | 649thof 2,826 | – |
| April 2023 | 519.2 µg/m³ | 563rdof 1,622 | – |
| September 2026 | 498.9 µg/m³ | 803rdof 2,981 | – |
| June 2025 | 498.8 µg/m³ | 1,652ndof 2,508 | – |
| June 2024 | 478.5 µg/m³ | 1,125thof 2,563 | – |
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.
Oceano's worst days
| Day | US AQI | Episode |
|---|---|---|
| 29 Jul 2023 | 14653.7 µg/m³ | – |
| 20 Sept 2023 | 9733.7 µg/m³ | California and Oregon, United States, September 2023 |
| 21 Sept 2023 | 9432.1 µg/m³ | California and Oregon, United States, September 2023 |
| 22 Sept 2023 | 9130.7 µg/m³ | California and Oregon, United States, September 2023 |
| 29 Aug 2023 | 8527.3 µg/m³ | North-western United States and Canada, August 2023 |
| 13 Sept 2026 | 8225.8 µg/m³ | – |
| 23 Sept 2023 | 8024.7 µg/m³ | California and Oregon, United States, September 2023 |
| 16 May 2026 | 7823.4 µg/m³ | – |
| 15 Jun 2024 | 7722.9 µg/m³ | – |
| 21 Jun 2025 | 7722.8 µg/m³ | – |
Daily means, the highest since 1 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, Oceano, United States, 1 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/oceano/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.
Oceano now: the last 24 hours, its ranks today and the last 12 months day by day.
Updated 2026-10-12 19:07 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).