SmogRank / Japan / Chiba / Ōami

Ōami, month by month

Ōami has a measured daily mean on 411 days since 29 July 2023. Its worst month was July 2026, at 51 US AQI (9.2 µg/m³), 1,562nd of 2,784 cities on that month's world ranking. Its cleanest was September 2026, at 28 US AQI (5.0 µg/m³).

Every month since 2023

202638 so far242 days measured2,281st of 2,791 in the world
Jan2 daysFeb46#1,912Mar40#2,314Apr41#1,809May39#1,623Jun28#2,148Jul51#1,562Aug36#2,334Sep28#2,339Oct33#1,886
2025too few days for a mean (a year needs 256)38 days measured
Jan4 daysFeb6 daysMar6 daysApr6 daysMay8 daysJun6 daysJul2 daysAugnoneSepnoneOctnoneNovnoneDecnone
2024too few days for a mean (a year needs 257)87 days measured
Jan6 daysFeb4 daysMar11 daysApr11 daysMay8 daysJun3 daysJul20 daysAug6 daysSep5 daysOct4 daysNov6 daysDec3 days
2023too few days for a mean (a year needs 256)44 days measured
JanFebMarAprMayJunJul2 daysAug10 daysSep3 daysOct8 daysNov10 daysDec11 days
Each square is a month's mean PM2.5 in US AQI from Ōami's measured days, with its place on that month's world ranking under it. A month has a mean once 70% of its days are measured, the rule the monthly rankings use; under that, the square gives the days measured. Each square opens that month's ranking with Ōami marked; each year, the year's. A dashed square is the running month, so far.
Good0–50
Moderate51–100
Sensitive groups101–150
Unhealthy151–200
Very unhealthy201–300
Hazardous301+

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

31 months
MonthWhy
Jan 20262 of 31 days measured; a month needs 22. The others: 29 with under 18 hours of readings or readings that failed our checks.
Dec 2025No day measured. The others: 31 with under 18 hours of readings or readings that failed our checks.
Nov 2025No day measured. The others: 30 with under 18 hours of readings or readings that failed our checks.
Oct 2025No day measured. The others: 31 with under 18 hours of readings or readings that failed our checks.
Sep 2025No day measured. The others: 30 with under 18 hours of readings or readings that failed our checks.
Aug 2025No day measured. The others: 31 with under 18 hours of readings or readings that failed our checks.
Jul 20252 of 31 days measured; a month needs 22. The others: 29 with under 18 hours of readings or readings that failed our checks.
Jun 20256 of 30 days measured; a month needs 21. The others: 24 with under 18 hours of readings or readings that failed our checks.
May 20258 of 31 days measured; a month needs 22. The others: 23 with under 18 hours of readings or readings that failed our checks.
Apr 20256 of 30 days measured; a month needs 21. The others: 24 with under 18 hours of readings or readings that failed our checks.
Mar 20256 of 31 days measured; a month needs 22. The others: 25 with under 18 hours of readings or readings that failed our checks.
Feb 20256 of 28 days measured; a month needs 20. The others: 22 with under 18 hours of readings or readings that failed our checks.
Jan 20254 of 31 days measured; a month needs 22. The others: 27 with under 18 hours of readings or readings that failed our checks.
Dec 20243 of 31 days measured; a month needs 22. The others: 28 with under 18 hours of readings or readings that failed our checks.
Nov 20246 of 30 days measured; a month needs 21. The others: 24 with under 18 hours of readings or readings that failed our checks.
Oct 20244 of 31 days measured; a month needs 22. The others: 27 with under 18 hours of readings or readings that failed our checks.
Sep 20245 of 30 days measured; a month needs 21. The others: 25 with under 18 hours of readings or readings that failed our checks.
Aug 20246 of 31 days measured; a month needs 22. The others: 25 with under 18 hours of readings or readings that failed our checks.
Jul 202420 of 31 days measured; a month needs 22. The others: 11 with under 18 hours of readings or readings that failed our checks.
Jun 20243 of 30 days measured; a month needs 21. The others: 27 with under 18 hours of readings or readings that failed our checks.
May 20248 of 31 days measured; a month needs 22. The others: 23 with under 18 hours of readings or readings that failed our checks.
Apr 202411 of 30 days measured; a month needs 21. The others: 19 with under 18 hours of readings or readings that failed our checks.
Mar 202411 of 31 days measured; a month needs 22. The others: 1 missing from OpenAQ's archive, 19 with under 18 hours of readings or readings that failed our checks.
Feb 20244 of 29 days measured; a month needs 21. The others: 1 missing from OpenAQ's archive, 24 with under 18 hours of readings or readings that failed our checks.
Jan 20246 of 31 days measured; a month needs 22. The others: 25 with under 18 hours of readings or readings that failed our checks.
Dec 202311 of 31 days measured; a month needs 22. The others: 20 with under 18 hours of readings or readings that failed our checks.
Nov 202310 of 30 days measured; a month needs 21. The others: 20 with under 18 hours of readings or readings that failed our checks.
Oct 20238 of 31 days measured; a month needs 22. The others: 23 with under 18 hours of readings or readings that failed our checks.
Sep 20233 of 30 days measured; a month needs 21. The others: 27 with under 18 hours of readings or readings that failed our checks.
Aug 202310 of 31 days measured; a month needs 22. The others: 21 with under 18 hours of readings or readings that failed our checks.
Jul 20232 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.

Ōami's worst months

MonthUS AQIDays measuredWorld rank
July 2026 519.2 µg/m³29 of 311,562ndof 2,784
February 2026 468.2 µg/m³27 of 281,912thof 2,866
April 2026 417.3 µg/m³28 of 301,809thof 2,941
March 2026 407.2 µg/m³28 of 312,314thof 2,971
May 2026 397.0 µg/m³28 of 311,623rdof 2,874
August 2026 366.4 µg/m³31 of 312,334thof 2,896

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.

Ōami's worst days

DayUS AQIEpisode
6 Jul 2025 12143.6 µg/m³Japan and South Korea, June and July 2025
13 Feb 2025 8929.4 µg/m³–
26 Mar 2025 8728.2 µg/m³Japan and South Korea, March 2025
16 Jul 2026 8024.7 µg/m³–
18 Apr 2024 8024.4 µg/m³–
20 May 2025 7723.2 µg/m³–
22 Jul 2024 7622.5 µg/m³–
1 Aug 2026 7321.1 µg/m³–
19 Apr 2024 7320.9 µg/m³–
2 Mar 2025 7120.0 µg/m³–

Daily means, the highest since 29 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, Ōami, Japan, 29 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/oami/history (accessed 12 Oct 2026).

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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.

Ōami now: the last 24 hours, its ranks today and the last 12 months day by day.

Updated 2026-10-12 18:07 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).