SmogRank / Japan / Kagawa / Tonoshō
Tonoshō, month by month
Tonoshō has a measured daily mean on 1,047 days since 28 July 2023. Its worst month was August 2025, at 56 US AQI (11.7 µg/m³), 846th of 2,901 cities on that month's world ranking. Its cleanest was October 2025, at 27 US AQI (4.8 µg/m³). 2025 averaged 46 US AQI (8.3 µg/m³), against 38 US AQI (6.8 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
6 months
| Month | Why |
|---|---|
| Jul 2026 | 21 of 31 days measured; a month needs 22. The others: 10 with readings for part of the day (a day needs 18 hours). |
| Jan 2026 | 20 of 31 days measured; a month needs 22. The others: 4 with no readings from the monitor, 7 with readings for part of the day (a day needs 18 hours). |
| Jan 2025 | 4 of 31 days measured; a month needs 22. The others: 1 with readings for part of the day (a day needs 18 hours), 26 with under 18 hours of readings or readings that failed our checks. |
| Dec 2024 | 16 of 31 days measured; a month needs 22. The others: 7 with no readings from the monitor, 8 with readings for part of the day (a day needs 18 hours). |
| Feb 2024 | 20 of 29 days measured; a month needs 21. The others: 1 with no readings from the monitor, 7 with readings for part of the day (a day needs 18 hours), 1 missing from OpenAQ's archive. |
| 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.
Tonoshō's worst months
| Month | US AQI | World rank | Episode |
|---|---|---|---|
| August 2025 | 5611.7 µg/m³ | 846thof 2,901 | – |
| March 2025 | 5410.6 µg/m³ | 1,490thof 2,862 | Japan and South Korea, March 2025 |
| April 2025 | 5410.5 µg/m³ | 1,054thof 2,951 | – |
| June 2025 | 5410.5 µg/m³ | 1,150thof 2,508 | Japan and South Korea, June and July 2025 |
| March 2026 | 5310.1 µg/m³ | 1,648thof 2,971 | Japan and South Korea, March 2026 |
| February 2026 | 529.9 µg/m³ | 1,418thof 2,866 | – |
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.
Tonoshō's worst days
| Day | US AQI | Episode |
|---|---|---|
| 22 Jul 2026 | 10537.0 µg/m³ | Japan and South Korea, July 2026 |
| 9 Jul 2025 | 9733.7 µg/m³ | Japan and South Korea, June and July 2025 |
| 18 Apr 2024 | 9532.9 µg/m³ | Japan and South Korea, April 2024 |
| 21 Jul 2026 | 9030.0 µg/m³ | Japan and South Korea, July 2026 |
| 29 Mar 2026 | 8426.7 µg/m³ | Japan and South Korea, March 2026 |
| 23 Jul 2026 | 8225.5 µg/m³ | Japan and South Korea, July 2026 |
| 26 Mar 2025 | 8125.2 µg/m³ | Japan and South Korea, March 2025 |
| 30 Mar 2026 | 7622.7 µg/m³ | Japan and South Korea, March 2026 |
| 2 Mar 2025 | 7522.2 µg/m³ | – |
| 24 Jul 2026 | 7522.1 µg/m³ | Japan and South Korea, July 2026 |
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, Tonoshō, 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/tonosho/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.
Tonoshō now: the last 24 hours, its ranks today and the last 12 months day by day.
Updated 2026-10-12 23:07 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).