SmogRank / Taiwan / Taiwan / Yilan
Yilan, month by month
Yilan has a measured daily mean on 834 days since 8 February 2024. Its worst month was April 2025, at 61 US AQI (14.4 µg/m³), 571st of 2,951 cities on that month's world ranking. Its cleanest was October 2024, at 23 US AQI (4.2 µg/m³).
Every month since 2024
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
5 months
| Month | Why |
|---|---|
| Nov 2025 | 12 of 30 days measured; a month needs 21. The others: 18 with under 18 hours of readings or readings that failed our checks. |
| Oct 2025 | 10 of 31 days measured; a month needs 22. The others: 21 with under 18 hours of readings or readings that failed our checks. |
| Aug 2025 | 6 of 31 days measured; a month needs 22. The others: 25 with under 18 hours of readings or readings that failed our checks. |
| Jul 2025 | No day measured. The others: 31 with under 18 hours of readings or readings that failed our checks. |
| Feb 2024 | 6 of 29 days measured; a month needs 21. The others: 16 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.
Yilan's worst months
| Month | US AQI | World rank |
|---|---|---|
| April 2025 | 6114.4 µg/m³ | 571stof 2,951 |
| April 2024 | 6114.2 µg/m³ | 468thof 2,520 |
| March 2024 | 5812.7 µg/m³ | 245thof 1,698 |
| April 2026 | 5612.0 µg/m³ | 723rdof 2,941 |
| January 2026 | 5611.9 µg/m³ | 931stof 2,617 |
| February 2026 | 5611.7 µg/m³ | 1,067thof 2,866 |
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.
Yilan's worst days
| Day | US AQI | Episode |
|---|---|---|
| 13 Apr 2025 | 9029.8 µg/m³ | – |
| 17 Feb 2025 | 8929.4 µg/m³ | Taiwan, 17 February 2025 |
| 28 Nov 2025 | 8527.3 µg/m³ | Taiwan, 28 November 2025 |
| 4 Apr 2024 | 8225.9 µg/m³ | – |
| 25 Nov 2025 | 8125.4 µg/m³ | Taiwan, 25 November 2025 |
| 7 Jan 2026 | 7823.4 µg/m³ | – |
| 8 Mar 2024 | 7622.7 µg/m³ | – |
| 21 Jan 2025 | 7622.4 µg/m³ | – |
| 6 Jan 2025 | 7522.0 µg/m³ | – |
| 30 Mar 2026 | 7421.7 µg/m³ | – |
Daily means, the highest since 8 Feb 2024; 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, Yilan, Taiwan, 8 Feb 2024 – 12 Oct 2026. Monitor data from Taiwan's Ministry of Environment via OpenAQ; sources listed at smogrank.com/sources. smogrank.com/tw/yilan/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.
Yilan now: the last 24 hours, its ranks today and the last 12 months day by day.
Updated 2026-10-12 19:07 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).