SmogRank / Japan / Miyazaki / Kobayashi
Kobayashi, month by month
Kobayashi has a measured daily mean on 1,120 days since 28 July 2023. Its worst month was July 2025, at 59 US AQI (13.3 µg/m³), 591st of 2,889 cities on that month's world ranking. Its cleanest was July 2024, at 29 US AQI (5.3 µg/m³). 2025 averaged 52 US AQI (9.6 µg/m³), against 46 US AQI (8.2 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 |
|---|---|
| Nov 2025 | 18 of 30 days measured; a month needs 21. The others: 12 with under 18 hours of readings or readings that failed our checks. |
| Jul 2023 | 3 of 31 days measured; a month needs 22. The others: 1 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.
Kobayashi's worst months
| Month | US AQI | World rank | Episode |
|---|---|---|---|
| July 2025 | 5913.3 µg/m³ | 591stof 2,889 | Japan and South Korea, June and July 2025 |
| July 2026 | 5812.8 µg/m³ | 756thof 2,784 | Japan and South Korea, July 2026 |
| August 2025 | 5611.7 µg/m³ | 846thof 2,901 | – |
| August 2024 | 5511.2 µg/m³ | 422ndof 2,010 | Miyazaki, Oita and Kumamoto, Japan, August 2024 |
| March 2025 | 5410.6 µg/m³ | 1,490thof 2,862 | – |
| November 2023 | 5410.5 µg/m³ | 510thof 2,243 | – |
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.
Kobayashi's worst days
| Day | US AQI | Episode |
|---|---|---|
| 4 Jul 2025 | 189109.0 µg/m³ | Japan and South Korea, June and July 2025 |
| 10 Aug 2025 | 14151.9 µg/m³ | – |
| 5 Jul 2025 | 11440.7 µg/m³ | Japan and South Korea, June and July 2025 |
| 25 Jul 2026 | 9633.5 µg/m³ | Japan and South Korea, July 2026 |
| 21 Jul 2026 | 9331.9 µg/m³ | Japan and South Korea, July 2026 |
| 11 Feb 2024 | 9331.5 µg/m³ | Japan, 11 to 12 February 2024 |
| 3 Jul 2025 | 8929.5 µg/m³ | Japan and South Korea, June and July 2025 |
| 28 Mar 2026 | 8828.7 µg/m³ | Japan and South Korea, March 2026 |
| 4 Aug 2024 | 8527.2 µg/m³ | Miyazaki, Oita and Kumamoto, Japan, August 2024 |
| 22 Jul 2026 | 8527.2 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, Kobayashi, 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/kobayashi/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.
Kobayashi 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).