SmogRank / Japan / Aichi / Seto
Seto, month by month
Seto has a measured daily mean on 1,108 days since 28 July 2023. Its worst month was July 2025, at 57 US AQI (12.4 µg/m³), 753rd of 2,889 cities on that month's world ranking. Its cleanest was January 2024, at 28 US AQI (5.1 µg/m³). 2025 averaged 49 US AQI (8.8 µg/m³), against 42 US AQI (7.5 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
1 month
| Month | Why |
|---|---|
| Jul 2023 | 4 of 31 days measured; a month needs 22. |
A day counts once 18 hours of it are measured; a month needs 70% of its days.
Seto's worst months
| Month | US AQI | World rank | Episode |
|---|---|---|---|
| July 2025 | 5712.4 µg/m³ | 753rdof 2,889 | Japan and South Korea, June and July 2025 |
| August 2025 | 5712.3 µg/m³ | 709thof 2,901 | – |
| April 2024 | 5511.0 µg/m³ | 866thof 2,520 | – |
| July 2026 | 5410.9 µg/m³ | 1,140thof 2,784 | – |
| June 2025 | 5410.6 µg/m³ | 1,118thof 2,508 | Japan and South Korea, June and July 2025 |
| March 2025 | 5410.5 µg/m³ | 1,514thof 2,862 | Japan and South Korea, March 2025 |
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.
Seto's worst days
| Day | US AQI | Episode |
|---|---|---|
| 26 Mar 2025 | 14954.9 µg/m³ | Japan and South Korea, March 2025 |
| 9 Jul 2025 | 9532.7 µg/m³ | Japan and South Korea, June and July 2025 |
| 5 Jul 2025 | 8829.1 µg/m³ | Japan and South Korea, June and July 2025 |
| 2 Jul 2025 | 8628.0 µg/m³ | Japan and South Korea, June and July 2025 |
| 3 Jul 2025 | 8527.3 µg/m³ | Japan and South Korea, June and July 2025 |
| 4 Aug 2025 | 8024.7 µg/m³ | – |
| 22 Jul 2026 | 7823.8 µg/m³ | – |
| 4 Nov 2023 | 7823.7 µg/m³ | – |
| 19 Apr 2024 | 7823.4 µg/m³ | – |
| 8 Jul 2025 | 7823.4 µg/m³ | Japan and South Korea, June and July 2025 |
Daily means, the highest since 28 Jul 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, Seto, Japan, 28 Jul 2023 – 12 Oct 2026. Monitor data from Ministry of the Environment Air Pollutant Wide Area Monitoring System via OpenAQ; sources listed at smogrank.com/sources. smogrank.com/jp/seto/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.
Seto now: the last 24 hours, its ranks today and the last 12 months day by day.
Updated 2026-10-12 17:07 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).