SmogRank / Japan / Chiba / Nagadomi
Nagadomi, month by month
Nagadomi has a measured daily mean on 751 days since 28 July 2023. Its worst month was July 2024, at 54 US AQI (10.8 µg/m³), 587th of 2,566 cities on that month's world ranking. Its cleanest was September 2023, at 27 US AQI (4.9 µg/m³). 2025 averaged 44 US AQI (7.9 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
16 months
| Month | Why |
|---|---|
| Oct 2026 | No day measured. The others: 13 with no readings from the monitor. |
| Sep 2026 | No day measured. The others: 30 with no readings from the monitor. |
| Aug 2026 | No day measured. The others: 31 with no readings from the monitor. |
| Jul 2026 | No day measured. The others: 31 with no readings from the monitor. |
| Jun 2026 | No day measured. The others: 30 with no readings from the monitor. |
| May 2026 | No day measured. The others: 31 with no readings from the monitor. |
| Apr 2026 | No day measured. The others: 30 with no readings from the monitor. |
| Mar 2026 | No day measured. The others: 31 with no readings from the monitor. |
| Feb 2026 | 13 of 28 days measured; a month needs 20. The others: 12 with no readings from the monitor, 3 with readings for part of the day (a day needs 18 hours). |
| Jan 2026 | 18 of 31 days measured; a month needs 22. The others: 4 with no readings from the monitor, 9 with readings for part of the day (a day needs 18 hours). |
| Oct 2024 | 21 of 31 days measured; a month needs 22. The others: 10 with under 18 hours of readings or readings that failed our checks. |
| Feb 2024 | 16 of 29 days measured; a month needs 21. The others: 1 missing from OpenAQ's archive, 12 with under 18 hours of readings or readings that failed our checks. |
| Jan 2024 | 21 of 31 days measured; a month needs 22. The others: 10 with under 18 hours of readings or readings that failed our checks. |
| Dec 2023 | 21 of 31 days measured; a month needs 22. The others: 10 with under 18 hours of readings or readings that failed our checks. |
| Aug 2023 | 17 of 31 days measured; a month needs 22. The others: 14 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.
Nagadomi's worst months
| Month | US AQI | World rank | Episode |
|---|---|---|---|
| July 2024 | 5410.8 µg/m³ | 587thof 2,566 | – |
| July 2025 | 5310.2 µg/m³ | 1,260thof 3,073 | Japan and South Korea, June and July 2025 |
| August 2025 | 5310.0 µg/m³ | 1,282ndof 3,095 | – |
| April 2024 | 519.1 µg/m³ | 1,150thof 2,520 | – |
| December 2025 | 498.9 µg/m³ | 1,703rdof 3,198 | – |
| March 2025 | 498.8 µg/m³ | 2,023rdof 3,102 | Japan and South Korea, March 2025 |
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.
Nagadomi's worst days
| Day | US AQI | Episode |
|---|---|---|
| 7 Jul 2025 | 10938.6 µg/m³ | Japan and South Korea, June and July 2025 |
| 6 Jul 2025 | 10436.8 µg/m³ | Japan and South Korea, June and July 2025 |
| 8 Jul 2025 | 9633.0 µg/m³ | Japan and South Korea, June and July 2025 |
| 26 Mar 2025 | 9030.1 µg/m³ | Japan and South Korea, March 2025 |
| 9 Jul 2025 | 9030.0 µg/m³ | Japan and South Korea, June and July 2025 |
| 30 Aug 2025 | 7924.1 µg/m³ | – |
| 20 May 2025 | 7823.6 µg/m³ | – |
| 18 Apr 2024 | 7723.0 µg/m³ | – |
| 3 Nov 2023 | 7421.5 µg/m³ | – |
| 10 Dec 2023 | 7421.2 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, Nagadomi, Japan, 28 Jul 2023 – 15 Feb 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/nagadomi/history (accessed 14 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.
Nagadomi now: the last 24 hours, its ranks today and the last 12 months day by day.
Updated 2026-10-14 03:07 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).