SmogRank / Japan / Ibaraki / Jōsō
Jōsō, month by month
Jōsō has a measured daily mean on 1,072 days since 28 July 2023. Its worst month was December 2025, at 61 US AQI (14.7 µg/m³), 750th of 3,006 cities on that month's world ranking. Its cleanest was September 2026, at 34 US AQI (6.2 µg/m³). 2025 averaged 53 US AQI (10.1 µg/m³), against 51 US AQI (9.1 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
3 months
| Month | Why |
|---|---|
| Jan 2026 | 19 of 31 days measured; a month needs 22. The others: 12 with under 18 hours of readings or readings that failed our checks. |
| Jul 2024 | 18 of 31 days measured; a month needs 22. The others: 13 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.
Jōsō's worst months
| Month | US AQI | World rank | Episode |
|---|---|---|---|
| December 2025 | 6114.7 µg/m³ | 750thof 3,006 | Japan, December 2025 |
| December 2023 | 6014.0 µg/m³ | 314thof 2,247 | Japan, 9 to 10 December 2023 |
| November 2023 | 5812.7 µg/m³ | 243rdof 2,243 | Japan, November 2023 |
| July 2025 | 5712.5 µg/m³ | 731stof 2,889 | Japan and South Korea, June and July 2025 |
| November 2025 | 5712.4 µg/m³ | 728thof 2,715 | – |
| February 2026 | 5712.3 µg/m³ | 990thof 2,866 | Japan, 14 to 15 February 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.
Jōsō's worst days
| Day | US AQI | Episode |
|---|---|---|
| 7 Jul 2025 | 13649.6 µg/m³ | Japan and South Korea, June and July 2025 |
| 9 Jul 2025 | 11842.5 µg/m³ | Japan and South Korea, June and July 2025 |
| 8 Jul 2025 | 11641.4 µg/m³ | Japan and South Korea, June and July 2025 |
| 21 Dec 2025 | 11440.9 µg/m³ | Japan, December 2025 |
| 20 Dec 2025 | 11039.0 µg/m³ | Japan, December 2025 |
| 25 Nov 2025 | 9532.5 µg/m³ | – |
| 6 Jul 2025 | 9432.3 µg/m³ | Japan and South Korea, June and July 2025 |
| 10 Dec 2023 | 9432.0 µg/m³ | Japan, 9 to 10 December 2023 |
| 4 Nov 2023 | 9331.8 µg/m³ | Japan, November 2023 |
| 15 Feb 2026 | 9231.0 µg/m³ | Japan, 14 to 15 February 2026 |
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, Jōsō, 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/joso/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.
Jōsō now: the last 24 hours, its ranks today and the last 12 months day by day.
Updated 2026-10-12 23:07 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).