SmogRank / Japan / Ibaraki / Chikusei
Chikusei, month by month
Chikusei has a measured daily mean on 1,144 days since 28 July 2023. Its worst month was July 2024, at 69 US AQI (18.7 µg/m³), 115th of 2,566 cities on that month's world ranking. Its cleanest was September 2026, at 31 US AQI (5.5 µg/m³). 2025 averaged 53 US AQI (10.4 µg/m³), against 55 US AQI (11.5 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
2 months
| Month | Why |
|---|---|
| Oct 2026 | 8 of 12 days measured; a month needs 9. The others: 1 with no readings from the monitor, 3 with readings for part of the day (a day needs 18 hours). |
| 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.
Chikusei's worst months
| Month | US AQI | World rank | Episode |
|---|---|---|---|
| July 2024 | 6918.7 µg/m³ | 115thof 2,566 | Japan, 12 to 14 July 2024 Japan, 6 to 8 July 2024 |
| December 2023 | 6516.8 µg/m³ | 237thof 2,247 | Japan, 9 to 10 December 2023 |
| November 2023 | 6214.9 µg/m³ | 150thof 2,243 | Japan, November 2023 |
| December 2025 | 6013.8 µg/m³ | 805thof 3,006 | Japan, December 2025 |
| February 2026 | 5812.9 µg/m³ | 928thof 2,866 | Japan, 14 to 15 February 2026 |
| August 2025 | 5812.7 µg/m³ | 633rdof 2,901 | Japan, 4 to 5 August 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.
Chikusei's worst days
| Day | US AQI | Episode |
|---|---|---|
| 9 Dec 2023 | 12444.9 µg/m³ | Japan, 9 to 10 December 2023 |
| 9 Jul 2025 | 11741.8 µg/m³ | Japan and South Korea, June and July 2025 |
| 7 Jul 2025 | 11139.5 µg/m³ | Japan and South Korea, June and July 2025 |
| 4 Nov 2023 | 10637.6 µg/m³ | Japan, November 2023 |
| 8 Jul 2025 | 10236.1 µg/m³ | Japan and South Korea, June and July 2025 |
| 8 Jul 2024 | 10035.4 µg/m³ | Japan, 6 to 8 July 2024 |
| 20 Dec 2025 | 10035.3 µg/m³ | Japan, December 2025 |
| 21 Dec 2025 | 9834.5 µg/m³ | Japan, December 2025 |
| 9 Jul 2024 | 9532.9 µg/m³ | – |
| 2 Nov 2023 | 9331.9 µg/m³ | Japan, November 2023 |
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, Chikusei, 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/chikusei/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.
Chikusei 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).