SmogRank / Japan / Miyazaki / Nichinan
Nichinan, month by month
Nichinan has a measured daily mean on 1,115 days since 28 July 2023. Its worst month was March 2025, at 56 US AQI (11.9 µg/m³), 1,252nd of 2,862 cities on that month's world ranking. Its cleanest was July 2024, at 32 US AQI (5.8 µg/m³). 2025 averaged 52 US AQI (9.5 µg/m³), against 49 US AQI (8.8 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
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.
Nichinan's worst months
| Month | US AQI | World rank | Episode |
|---|---|---|---|
| March 2025 | 5611.9 µg/m³ | 1,252ndof 2,862 | – |
| August 2024 | 5611.8 µg/m³ | 360thof 2,010 | – |
| April 2025 | 5611.6 µg/m³ | 822ndof 2,951 | – |
| November 2023 | 5511.4 µg/m³ | 375thof 2,243 | – |
| July 2026 | 5511.3 µg/m³ | 1,051stof 2,784 | – |
| March 2026 | 5410.9 µg/m³ | 1,446thof 2,971 | Japan and South Korea, March 2026 |
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.
Nichinan's worst days
| Day | US AQI | Episode |
|---|---|---|
| 11 Feb 2024 | 9130.5 µg/m³ | Japan, 11 to 12 February 2024 |
| 29 Mar 2026 | 9030.1 µg/m³ | Japan and South Korea, March 2026 |
| 5 Jul 2025 | 8728.5 µg/m³ | Japan and South Korea, June and July 2025 |
| 4 Sept 2024 | 8527.6 µg/m³ | Japan and South Korea, September 2024 |
| 25 Sept 2026 | 7924.3 µg/m³ | – |
| 26 Jul 2026 | 7923.9 µg/m³ | – |
| 19 Apr 2024 | 7823.7 µg/m³ | – |
| 28 Mar 2026 | 7722.8 µg/m³ | Japan and South Korea, March 2026 |
| 4 Jul 2025 | 7521.9 µg/m³ | Japan and South Korea, June and July 2025 |
| 22 Jul 2026 | 7521.8 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, Nichinan, Japan, 28 Jul 2023 – 10 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/nichinan/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.
Nichinan 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).