SmogRank / Japan / Kumamoto / Iwashita
Iwashita, month by month
Iwashita has a measured daily mean on 1,011 days since 28 July 2023. Its worst month was March 2026, at 57 US AQI (12.5 µg/m³), 1,124th of 2,971 cities on that month's world ranking. Its cleanest was October 2024, at 31 US AQI (5.6 µg/m³).
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
5 months
| Month | Why |
|---|---|
| Apr 2024 | 5 of 30 days measured; a month needs 21. The others: 25 with under 18 hours of readings or readings that failed our checks. |
| Mar 2024 | No day measured. The others: 1 missing from OpenAQ's archive, 30 with under 18 hours of readings or readings that failed our checks. |
| Feb 2024 | No day measured. The others: 1 missing from OpenAQ's archive, 28 with under 18 hours of readings or readings that failed our checks. |
| Jan 2024 | No day measured. The others: 31 with under 18 hours of readings or readings that failed our checks. |
| 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.
Iwashita's worst months
| Month | US AQI | World rank | Episode |
|---|---|---|---|
| March 2026 | 5712.5 µg/m³ | 1,124thof 2,971 | Japan and South Korea, March 2026 |
| July 2025 | 5712.2 µg/m³ | 791stof 2,889 | Japan and South Korea, June and July 2025 |
| August 2025 | 5511.1 µg/m³ | 974thof 2,901 | – |
| May 2024 | 5511.0 µg/m³ | 595thof 2,684 | Japan, May 2024 |
| May 2026 | 5511.0 µg/m³ | 656thof 2,874 | – |
| August 2024 | 5410.8 µg/m³ | 478thof 2,010 | – |
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.
Iwashita's worst days
| Day | US AQI | Episode |
|---|---|---|
| 2 Jul 2025 | 14352.6 µg/m³ | Japan and South Korea, June and July 2025 |
| 3 Jul 2025 | 12545.2 µg/m³ | Japan and South Korea, June and July 2025 |
| 1 Jul 2025 | 10938.9 µg/m³ | Japan and South Korea, June and July 2025 |
| 4 Jul 2025 | 10436.9 µg/m³ | Japan and South Korea, June and July 2025 |
| 29 Mar 2026 | 9030.0 µg/m³ | Japan and South Korea, March 2026 |
| 28 Mar 2026 | 8828.9 µg/m³ | Japan and South Korea, March 2026 |
| 25 May 2024 | 8426.8 µg/m³ | Japan, May 2024 |
| 4 Sept 2024 | 8225.7 µg/m³ | Japan and South Korea, September 2024 |
| 30 Jun 2025 | 8125.3 µg/m³ | Japan and South Korea, June and July 2025 |
| 30 Aug 2025 | 8024.6 µg/m³ | – |
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, Iwashita, 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/iwashita/history (accessed 13 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.
Iwashita now: the last 24 hours, its ranks today and the last 12 months day by day.
Updated 2026-10-13 04:07 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).