SmogRank / Japan / Ehime / Niihama
Niihama, month by month
Niihama has a measured daily mean on 1,157 days since 28 July 2023. Its worst month was April 2024, at 68 US AQI (18.4 µg/m³), 282nd of 2,520 cities on that month's world ranking. Its cleanest was January 2024, at 43 US AQI (7.7 µg/m³). 2025 averaged 57 US AQI (12.5 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
1 month
| Month | Why |
|---|---|
| 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.
Niihama's worst months
| Month | US AQI | World rank | Episode |
|---|---|---|---|
| April 2024 | 6818.4 µg/m³ | 282ndof 2,520 | Japan and South Korea, April 2024 |
| March 2025 | 6617.3 µg/m³ | 747thof 2,862 | Japan and South Korea, March 2025 Japan, March 2025and 1 more |
| July 2025 | 6315.6 µg/m³ | 361stof 2,889 | Japan and South Korea, June and July 2025 |
| June 2025 | 6215.1 µg/m³ | 433rdof 2,508 | Japan and South Korea, June and July 2025 |
| April 2025 | 6014.0 µg/m³ | 588thof 2,951 | – |
| May 2024 | 6013.8 µg/m³ | 343rdof 2,684 | Japan, May 2024 South Korea and Japan, May 2024 |
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.
Niihama's worst days
| Day | US AQI | Episode |
|---|---|---|
| 2 Mar 2025 | 15257.3 µg/m³ | Japan and South Korea, February and March 2025 |
| 4 Jul 2025 | 15155.8 µg/m³ | Japan and South Korea, June and July 2025 |
| 3 Jul 2025 | 13448.8 µg/m³ | Japan and South Korea, June and July 2025 |
| 1 Mar 2025 | 12745.9 µg/m³ | Japan and South Korea, February and March 2025 |
| 15 Feb 2024 | 12143.6 µg/m³ | Japan, 14 to 15 February 2024 |
| 18 Apr 2024 | 11039.3 µg/m³ | Japan and South Korea, April 2024 |
| 19 Apr 2024 | 10938.8 µg/m³ | Japan and South Korea, April 2024 |
| 2 Jul 2025 | 10537.3 µg/m³ | Japan and South Korea, June and July 2025 |
| 27 Mar 2025 | 10537.1 µg/m³ | Japan and South Korea, March 2025 Japan, March 2025 |
| 28 Feb 2025 | 10436.6 µg/m³ | Japan and South Korea, February and 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, Niihama, 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/niihama/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.
Niihama now: the last 24 hours, its ranks today and the last 12 months day by day.
Updated 2026-10-12 22:07 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).