SmogRank / Japan / Osaka / Yao
Yao, month by month
Yao has a measured daily mean on 954 days since 28 July 2023. Its worst month was March 2025, at 59 US AQI (13.4 µg/m³), 1,081st of 2,862 cities on that month's world ranking. Its cleanest was September 2026, at 32 US AQI (5.7 µg/m³).
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
9 months
| Month | Why |
|---|---|
| Jan 2026 | 20 of 31 days measured; a month needs 22. The others: 11 with under 18 hours of readings or readings that failed our checks. |
| Apr 2024 | 6 of 30 days measured; a month needs 21. The others: 24 with under 18 hours of readings or readings that failed our checks. |
| Mar 2024 | No day measured. The others: 1 missing from OpenAQ's archive, 30 with under 18 hours of readings or readings that failed our checks. |
| Feb 2024 | No day measured. The others: 1 missing from OpenAQ's archive, 28 with under 18 hours of readings or readings that failed our checks. |
| Jan 2024 | No day measured. The others: 31 with under 18 hours of readings or readings that failed our checks. |
| Dec 2023 | No day measured. The others: 31 with under 18 hours of readings or readings that failed our checks. |
| Nov 2023 | No day measured. The others: 30 with under 18 hours of readings or readings that failed our checks. |
| Oct 2023 | 15 of 31 days measured; a month needs 22. The others: 16 with under 18 hours of readings or readings that failed our checks. |
| Jul 2023 | 4 of 31 days measured; a month needs 22. |
A day counts once 18 hours of it are measured; a month needs 70% of its days.
Yao's worst months
| Month | US AQI | World rank | Episode |
|---|---|---|---|
| March 2025 | 5913.4 µg/m³ | 1,081stof 2,862 | Japan and South Korea, March 2025 Japan and South Korea, February and March 2025 |
| July 2025 | 5812.9 µg/m³ | 662ndof 2,889 | Japan and South Korea, June and July 2025 |
| April 2025 | 5712.5 µg/m³ | 707thof 2,951 | – |
| August 2025 | 5611.9 µg/m³ | 789thof 2,901 | – |
| February 2026 | 5611.8 µg/m³ | 1,048thof 2,866 | – |
| July 2026 | 5611.8 µg/m³ | 929thof 2,784 | Japan and South Korea, July 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.
Yao's worst days
| Day | US AQI | Episode |
|---|---|---|
| 2 Mar 2025 | 11943.0 µg/m³ | Japan and South Korea, February and March 2025 |
| 4 Jul 2025 | 11943.0 µg/m³ | Japan and South Korea, June and July 2025 |
| 5 Jul 2025 | 10838.5 µg/m³ | Japan and South Korea, June and July 2025 |
| 3 Jul 2025 | 9633.4 µg/m³ | Japan and South Korea, June and July 2025 |
| 31 Jan 2025 | 9231.0 µg/m³ | Japan and South Korea, 31 January to 1 February 2025 |
| 26 Mar 2025 | 9230.9 µg/m³ | Japan and South Korea, March 2025 |
| 1 Feb 2025 | 9130.5 µg/m³ | Japan and South Korea, 31 January to 1 February 2025 |
| 28 Feb 2025 | 8829.2 µg/m³ | Japan and South Korea, February and March 2025 |
| 9 Jul 2025 | 8627.9 µg/m³ | Japan and South Korea, June and July 2025 |
| 24 Mar 2025 | 8226.0 µg/m³ | Japan and South Korea, March 2025 |
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, Yao, 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/yao/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.
Yao 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).