SmogRank / Japan / Kumamoto

Air quality in Kotō

Kumamoto, Japan. PM2.5 from 3 reference monitors, updated hourly.

12.0µg/m³
Moderate

Latest hour (16:00 UTC), 0.8× the WHO 24-hour guideline.

Rank, worst first

24 hours–not enough data
7 days#555of 2,330, at 9.7 µg/m³
30 days#531of 2,324, at 8.6 µg/m³
This year#702of 2,173, at 9.8 µg/m³

Why it ranks here

Likely volcanic emissions. On Sep 25, when Kotō averaged 18.4 µg/m³ (its typical day: 10.0), the Tokyo Volcanic Ash Advisory Centre issued 6 ash advisories for Sakurajima (Aira Caldera), 131 km away, with ash seen in satellite images. Volcanic gas and ash are a likely contributor; we don't check which way the wind blew, and advisories track ash for aircraft, often well above the ground.

Based on Kotō's own measurements, with volcanic ash advisories from the Tokyo (JMA) and Washington (NOAA) VAACs; causes are the usual kinds for a pattern like this, not a confirmed source.

The last 12 months, day by day

1102031Nov 2025DecJan 2026FebMarAprMayJunJulAugSepOct2025-11-01: 6.6 µg/m³2025-11-02: 8.5 µg/m³2025-11-03: 5.3 µg/m³2025-11-04: 11.1 µg/m³2025-11-05: 16.1 µg/m³2025-11-06: 11.2 µg/m³2025-11-07: 12.5 µg/m³2025-11-08: 14.1 µg/m³2025-11-09: 9.1 µg/m³2025-11-10: 12.2 µg/m³2025-11-11: 12.9 µg/m³2025-11-12: 15.6 µg/m³2025-11-13: 19.1 µg/m³2025-11-14: 15.0 µg/m³2025-11-15: 15.8 µg/m³2025-11-16: 20.8 µg/m³2025-11-17: 21.7 µg/m³2025-11-18: 10.7 µg/m³2025-11-19: 12.8 µg/m³2025-11-20: 10.6 µg/m³2025-11-21: 13.8 µg/m³2025-11-22: 8.8 µg/m³2025-11-23: 9.8 µg/m³2025-11-24: 14.5 µg/m³2025-11-25: 13.4 µg/m³2025-11-26: 15.6 µg/m³2025-11-27: 15.5 µg/m³2025-11-28: 12.5 µg/m³2025-11-29: 10.9 µg/m³2025-11-30: 10.6 µg/m³2025-12-01: 6.6 µg/m³2025-12-02: 13.2 µg/m³2025-12-03: 10.3 µg/m³2025-12-04: 7.7 µg/m³2025-12-05: 8.1 µg/m³2025-12-06: 9.1 µg/m³2025-12-07: 10.2 µg/m³2025-12-08: 16.1 µg/m³2025-12-09: 13.5 µg/m³2025-12-10: 12.7 µg/m³2025-12-11: 15.9 µg/m³2025-12-12: 11.3 µg/m³2025-12-13: 12.7 µg/m³2025-12-14: 8.0 µg/m³2025-12-15: 9.0 µg/m³2025-12-16: 12.2 µg/m³2025-12-17: 13.1 µg/m³2025-12-18: 17.6 µg/m³2025-12-19: 13.9 µg/m³2025-12-20: 14.3 µg/m³2025-12-21: 13.0 µg/m³2025-12-22: 4.6 µg/m³2025-12-23: 8.1 µg/m³2025-12-24: 10.4 µg/m³2025-12-25: 6.4 µg/m³2025-12-26: 6.5 µg/m³2025-12-27: 8.6 µg/m³2025-12-28: 11.8 µg/m³2025-12-29: 13.0 µg/m³2025-12-30: 15.1 µg/m³2025-12-31: 12.0 µg/m³2026-01-01: 6.7 µg/m³2026-01-02: 4.8 µg/m³2026-01-03: 5.6 µg/m³2026-01-04: 11.8 µg/m³2026-01-05: 13.6 µg/m³2026-01-06: 9.6 µg/m³2026-01-07: 11.4 µg/m³2026-01-08: 8.8 µg/m³2026-01-09: 8.6 µg/m³2026-01-10: 10.0 µg/m³2026-01-11: 7.3 µg/m³2026-01-12: 10.4 µg/m³2026-01-13: 12.3 µg/m³2026-01-14: 11.2 µg/m³2026-01-15: 16.5 µg/m³2026-01-16: 14.6 µg/m³2026-01-17: 17.4 µg/m³2026-01-18: 19.6 µg/m³2026-01-19: no data2026-01-20: 10.3 µg/m³2026-01-21: 5.8 µg/m³2026-01-22: 6.3 µg/m³2026-01-23: 8.5 µg/m³2026-01-24: no data2026-01-25: no data2026-01-26: 8.8 µg/m³2026-01-27: 14.4 µg/m³2026-01-28: 11.9 µg/m³2026-01-29: no data2026-01-30: 13.5 µg/m³2026-01-31: 10.8 µg/m³2026-02-01: 17.2 µg/m³2026-02-02: 15.6 µg/m³2026-02-03: 14.3 µg/m³2026-02-04: 12.2 µg/m³2026-02-05: 10.9 µg/m³2026-02-06: 16.0 µg/m³2026-02-07: 13.1 µg/m³2026-02-08: 8.4 µg/m³2026-02-09: 11.5 µg/m³2026-02-10: 14.1 µg/m³2026-02-11: 10.1 µg/m³2026-02-12: 17.1 µg/m³2026-02-13: 14.3 µg/m³2026-02-14: 17.5 µg/m³2026-02-15: 15.2 µg/m³2026-02-16: 19.6 µg/m³2026-02-17: 11.4 µg/m³2026-02-18: 12.0 µg/m³2026-02-19: 20.8 µg/m³2026-02-20: no data2026-02-21: no data2026-02-22: no data2026-02-23: no data2026-02-24: no data2026-02-25: 8.4 µg/m³2026-02-26: 6.5 µg/m³2026-02-27: 8.1 µg/m³2026-02-28: 5.1 µg/m³2026-03-01: 10.3 µg/m³2026-03-02: 9.4 µg/m³2026-03-03: 3.4 µg/m³2026-03-04: 5.7 µg/m³2026-03-05: 9.2 µg/m³2026-03-06: 10.6 µg/m³2026-03-07: 12.9 µg/m³2026-03-08: 12.4 µg/m³2026-03-09: 13.1 µg/m³2026-03-10: 18.2 µg/m³2026-03-11: 13.3 µg/m³2026-03-12: 12.9 µg/m³2026-03-13: 7.5 µg/m³2026-03-14: 5.7 µg/m³2026-03-15: 7.1 µg/m³2026-03-16: 16.2 µg/m³2026-03-17: 16.3 µg/m³2026-03-18: 19.0 µg/m³2026-03-19: 10.0 µg/m³2026-03-20: 16.1 µg/m³2026-03-21: 12.8 µg/m³2026-03-22: 13.5 µg/m³2026-03-23: 7.0 µg/m³2026-03-24: 14.5 µg/m³2026-03-25: 8.7 µg/m³2026-03-26: 9.4 µg/m³2026-03-27: 18.4 µg/m³2026-03-28: 30.5 µg/m³2026-03-29: 31.6 µg/m³2026-03-30: 16.3 µg/m³2026-03-31: 8.3 µg/m³2026-04-01: 5.8 µg/m³2026-04-02: 12.4 µg/m³2026-04-03: 13.2 µg/m³2026-04-04: 9.6 µg/m³2026-04-05: 12.8 µg/m³2026-04-06: 18.7 µg/m³2026-04-07: 11.9 µg/m³2026-04-08: 11.3 µg/m³2026-04-09: 12.9 µg/m³2026-04-10: 9.0 µg/m³2026-04-11: 10.4 µg/m³2026-04-12: 13.8 µg/m³2026-04-13: 9.7 µg/m³2026-04-14: 7.6 µg/m³2026-04-15: 4.9 µg/m³2026-04-16: 8.8 µg/m³2026-04-17: 10.6 µg/m³2026-04-18: 8.6 µg/m³2026-04-19: 6.8 µg/m³2026-04-20: 7.9 µg/m³2026-04-21: 10.0 µg/m³2026-04-22: 13.2 µg/m³2026-04-23: 3.7 µg/m³2026-04-24: 5.2 µg/m³2026-04-25: 7.4 µg/m³2026-04-26: 6.1 µg/m³2026-04-27: 9.0 µg/m³2026-04-28: 11.5 µg/m³2026-04-29: 12.3 µg/m³2026-04-30: 5.8 µg/m³2026-05-01: 12.9 µg/m³2026-05-02: 17.3 µg/m³2026-05-03: 10.4 µg/m³2026-05-04: 9.1 µg/m³2026-05-05: 13.6 µg/m³2026-05-06: 13.5 µg/m³2026-05-07: 8.4 µg/m³2026-05-08: 8.8 µg/m³2026-05-09: 9.5 µg/m³2026-05-10: 13.9 µg/m³2026-05-11: 13.7 µg/m³2026-05-12: 8.9 µg/m³2026-05-13: 4.6 µg/m³2026-05-14: 11.4 µg/m³2026-05-15: 12.5 µg/m³2026-05-16: 16.0 µg/m³2026-05-17: 20.1 µg/m³2026-05-18: 18.3 µg/m³2026-05-19: 11.3 µg/m³2026-05-20: 3.9 µg/m³2026-05-21: 4.8 µg/m³2026-05-22: 8.7 µg/m³2026-05-23: 15.0 µg/m³2026-05-24: 10.3 µg/m³2026-05-25: 5.0 µg/m³2026-05-26: 3.8 µg/m³2026-05-27: 3.4 µg/m³2026-05-28: 4.5 µg/m³2026-05-29: 11.6 µg/m³2026-05-30: 14.4 µg/m³2026-05-31: 23.1 µg/m³2026-06-01: 23.5 µg/m³2026-06-02: 2.9 µg/m³2026-06-03: 6.0 µg/m³2026-06-04: 5.4 µg/m³2026-06-05: 7.7 µg/m³2026-06-06: 13.7 µg/m³2026-06-07: 3.0 µg/m³2026-06-08: 7.2 µg/m³2026-06-09: 8.4 µg/m³2026-06-10: 9.3 µg/m³2026-06-11: 11.3 µg/m³2026-06-12: 10.1 µg/m³2026-06-13: 9.4 µg/m³2026-06-14: 10.5 µg/m³2026-06-15: 4.6 µg/m³2026-06-16: 3.2 µg/m³2026-06-17: 5.5 µg/m³2026-06-18: 5.1 µg/m³2026-06-19: 4.2 µg/m³2026-06-20: 4.7 µg/m³2026-06-21: 6.1 µg/m³2026-06-22: 7.8 µg/m³2026-06-23: 3.3 µg/m³2026-06-24: 2.1 µg/m³2026-06-25: 5.4 µg/m³2026-06-26: 2.0 µg/m³2026-06-27: 5.5 µg/m³2026-06-28: 6.9 µg/m³2026-06-29: 8.9 µg/m³2026-06-30: 12.2 µg/m³2026-07-01: 3.3 µg/m³2026-07-02: 2.9 µg/m³2026-07-03: 4.1 µg/m³2026-07-04: 6.0 µg/m³2026-07-05: 4.0 µg/m³2026-07-06: 4.2 µg/m³2026-07-07: 6.6 µg/m³2026-07-08: 8.0 µg/m³2026-07-09: 5.5 µg/m³2026-07-10: 6.5 µg/m³2026-07-11: 4.0 µg/m³2026-07-12: 9.1 µg/m³2026-07-13: 11.3 µg/m³2026-07-14: 8.3 µg/m³2026-07-15: 8.7 µg/m³2026-07-16: 8.0 µg/m³2026-07-17: 9.7 µg/m³2026-07-18: 10.7 µg/m³2026-07-19: 10.0 µg/m³2026-07-20: 9.1 µg/m³2026-07-21: 9.9 µg/m³2026-07-22: 10.5 µg/m³2026-07-23: 9.2 µg/m³2026-07-24: 11.7 µg/m³2026-07-25: 10.3 µg/m³2026-07-26: 7.2 µg/m³2026-07-27: 8.9 µg/m³2026-07-28: no data2026-07-29: 4.5 µg/m³2026-07-30: 5.6 µg/m³2026-07-31: 6.5 µg/m³2026-08-01: 9.4 µg/m³2026-08-02: 15.0 µg/m³2026-08-03: 18.1 µg/m³2026-08-04: 15.7 µg/m³2026-08-05: 6.3 µg/m³2026-08-06: 5.7 µg/m³2026-08-07: 5.6 µg/m³2026-08-08: 4.9 µg/m³2026-08-09: 4.5 µg/m³2026-08-10: 6.8 µg/m³2026-08-11: 8.9 µg/m³2026-08-12: 9.2 µg/m³2026-08-13: 12.0 µg/m³2026-08-14: 12.6 µg/m³2026-08-15: 9.3 µg/m³2026-08-16: 9.1 µg/m³2026-08-17: 7.9 µg/m³2026-08-18: 5.6 µg/m³2026-08-19: 5.4 µg/m³2026-08-20: 4.7 µg/m³2026-08-21: 5.0 µg/m³2026-08-22: 7.8 µg/m³2026-08-23: 9.2 µg/m³2026-08-24: 7.4 µg/m³2026-08-25: 4.9 µg/m³2026-08-26: 2.9 µg/m³2026-08-27: 5.0 µg/m³2026-08-28: 7.9 µg/m³2026-08-29: 8.0 µg/m³2026-08-30: 6.5 µg/m³2026-08-31: 15.0 µg/m³2026-09-01: 6.4 µg/m³2026-09-02: 4.2 µg/m³2026-09-03: 3.7 µg/m³2026-09-04: 1.7 µg/m³2026-09-05: 4.0 µg/m³2026-09-06: 7.2 µg/m³2026-09-07: 4.9 µg/m³2026-09-08: 6.3 µg/m³2026-09-09: 4.8 µg/m³2026-09-10: 8.5 µg/m³2026-09-11: 10.1 µg/m³2026-09-12: 12.4 µg/m³2026-09-13: 10.0 µg/m³2026-09-14: 5.9 µg/m³2026-09-15: 8.7 µg/m³2026-09-16: 13.6 µg/m³2026-09-17: 12.3 µg/m³2026-09-18: 4.4 µg/m³2026-09-19: 6.5 µg/m³2026-09-20: 7.5 µg/m³2026-09-21: 7.4 µg/m³2026-09-22: 11.4 µg/m³2026-09-23: 16.5 µg/m³2026-09-24: 17.9 µg/m³2026-09-25: 18.4 µg/m³. Likely volcanic emissions2026-09-26: 11.9 µg/m³2026-09-27: 3.4 µg/m³2026-09-28: 5.4 µg/m³2026-09-29: 6.6 µg/m³2026-09-30: 12.6 µg/m³2026-10-01: no data
47 of 352 measured days were over the WHO 24-hour guideline (15 µg/m³). One row per month, one square per local day; outlined days are named in the notes above.
Good0–9.0
Moderate9.1–35.4
Sensitive groups35.5–55.4
Unhealthy55.5–125.4
Very unhealthy125.5–225.4
Hazardous225.5+

Last 4 days, hour by hour

15302026-09-30 23:00 UTC: 14.0 µg/m³2026-10-01 00:00 UTC: 16.0 µg/m³2026-10-01 01:00 UTC: 17.0 µg/m³2026-10-01 02:00 UTC: 14.0 µg/m³2026-10-01 03:00 UTC: 15.0 µg/m³2026-10-01 04:00 UTC: 16.0 µg/m³2026-10-01 05:00 UTC: 14.0 µg/m³2026-10-01 06:00 UTC: 8.0 µg/m³2026-10-01 07:00 UTC: 11.0 µg/m³2026-10-01 08:00 UTC: 13.0 µg/m³2026-10-01 09:00 UTC: 14.0 µg/m³2026-10-01 10:00 UTC: 13.0 µg/m³2026-10-01 11:00 UTC: 13.0 µg/m³2026-10-01 12:00 UTC: 13.0 µg/m³2026-10-01 13:00 UTC: 12.0 µg/m³2026-10-01 16:00 UTC: 12.0 µg/m³Sep 28Sep 29Sep 30Oct 1
Times in UTC. Dashed line: WHO 24-hour guideline (15 µg/m³).

Its world rank, day by day

#1#2295NovDecJanFebMarAprMayJunJulAugSep
Rank on each day's board (1 = most polluted city that day).

2026 against 2025, month by month

15Jan 2025: 14.3 µg/m³Jan 2026: 10.8 µg/m³JanFeb 2025: 11.0 µg/m³Feb 2026: 13.0 µg/m³FebMar 2025: 12.3 µg/m³Mar 2026: 12.9 µg/m³MarApr 2025: 12.0 µg/m³Apr 2026: 9.7 µg/m³AprMay 2025: 11.2 µg/m³May 2026: 11.1 µg/m³MayJun 2025: 9.9 µg/m³Jun 2026: 7.2 µg/m³JunJul 2025: 12.3 µg/m³Jul 2026: 7.5 µg/m³JulAug 2025: 10.8 µg/m³Aug 2026: 8.3 µg/m³AugSep 2025: 6.8 µg/m³Sep 2026: 8.5 µg/m³SepOct 2025: 11.0 µg/m³OctNov 2025: 12.9 µg/m³NovDec 2025: 11.1 µg/m³Dec
Faded bars: 2025. A month shows once it has 10 measured days.

This week against past years

This weekThis week: 9.7 µg/m³9.720252025: 8.2 µg/m³8.220242024: 11.2 µg/m³11.220232023: 9.1 µg/m³9.1
Mean PM2.5 for 25 Sept to 1 Oct in each year. Dashed line: WHO 24-hour guideline.

Monitors

StationOperatorType
上益城郡益城町惣領１４７０政府標準利用規約（第2.0版） (Government Standard Terms of Use v2.0)Ministry of the Environment Air Pollutant Wide Area Monitoring SystemReference
熊本市南区城南町高482政府標準利用規約（第2.0版） (Government Standard Terms of Use v2.0)Ministry of the Environment Air Pollutant Wide Area Monitoring SystemReference
熊本市東区秋津3丁目1856政府標準利用規約（第2.0版） (Government Standard Terms of Use v2.0)Ministry of the Environment Air Pollutant Wide Area Monitoring SystemReference

The city's value is the median of its reference monitors each hour; low-cost sensors are listed but not counted when reference monitors exist. Data via OpenAQ; licences as listed. How we rank. Embed this on your site.

Other cities in Japan

30-day averages, µg/m³. All of Japan.

Updated 2026-10-01 18:07 UTC. Values are PM2.5 in µg/m³ (fine particles), the median of each city's monitors.