SmogRank / Japan / Hokkaido / Tōma
Tōma, month by month
Tōma, Hokkaido has a measured daily mean on 1,074 days since 28 July 2023. Its worst month was July 2024, at 55 US AQI (11.5 µg/m³), 489th of 2,566 cities on that month's world ranking. Its cleanest was September 2024, at 24 US AQI (4.3 µg/m³). 2025 averaged 38 US AQI (6.8 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
3 months
| Month | Why |
|---|---|
| Oct 2026 | 4 of 12 days measured; a month needs 9. The others: 7 with no readings from the monitor, 1 with readings for part of the day (a day needs 18 hours). |
| Sep 2025 | 14 of 30 days measured; a month needs 21. The others: 16 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.
Tōma's worst months
| Month | US AQI | World rank | Episode |
|---|---|---|---|
| July 2024 | 5511.5 µg/m³ | 489thof 2,566 | Japan, 12 to 14 July 2024 |
| February 2024 | 5310.1 µg/m³ | 640thof 2,486 | Hokkaido and Aomori, Japan, February 2024 |
| March 2026 | 5310.0 µg/m³ | 1,675thof 2,971 | – |
| January 2025 | 519.3 µg/m³ | 1,124thof 2,474 | – |
| January 2024 | 519.2 µg/m³ | 990thof 2,385 | – |
| April 2024 | 478.4 µg/m³ | 1,248thof 2,520 | – |
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.
Tōma's worst days
| Day | US AQI | Episode |
|---|---|---|
| 23 Dec 2024 | 10838.2 µg/m³ | – |
| 14 Feb 2024 | 9432.0 µg/m³ | Hokkaido and Aomori, Japan, February 2024 |
| 11 Jul 2024 | 9130.5 µg/m³ | – |
| 12 Jul 2024 | 8728.6 µg/m³ | Japan, 12 to 14 July 2024 |
| 18 Jul 2024 | 8628.1 µg/m³ | – |
| 6 Feb 2024 | 8628.0 µg/m³ | – |
| 5 Sept 2026 | 8628.0 µg/m³ | – |
| 6 Dec 2023 | 8627.8 µg/m³ | – |
| 16 Jul 2024 | 8326.5 µg/m³ | – |
| 6 Nov 2025 | 8225.5 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, Tōma, Hokkaido, Japan, 28 Jul 2023 – 4 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/toma/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.
Tōma now: the last 24 hours, its ranks today and the last 12 months day by day.
Updated 2026-10-12 22:07 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).