SmogRank / South Korea / Chungcheongnam-do / Cheonan
Cheonan, month by month
Cheonan has a measured daily mean on 918 days since 23 March 2024. Its worst month was March 2026, at 92 US AQI (30.9 µg/m³), 250th of 2,971 cities on that month's world ranking. Its cleanest was July 2024, at 51 US AQI (9.1 µg/m³). 2025 averaged 67 US AQI (17.8 µg/m³), against 63 US AQI (15.6 µg/m³) in 2024.
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
1 month
| Month | Why |
|---|---|
| Mar 2024 | 9 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.
Cheonan's worst months
| Month | US AQI | World rank | Episode |
|---|---|---|---|
| March 2026 | 9230.9 µg/m³ | 250thof 2,971 | Japan and South Korea, March 2026 South Korea, 15 to 18 March 2026 |
| March 2025 | 8326.5 µg/m³ | 391stof 2,862 | South Korea, 9 to 11 March 2025 |
| January 2025 | 8225.8 µg/m³ | 149thof 2,474 | Japan and South Korea, 17 to 24 January 2025 South Korea, 13 to 14 January 2025 |
| February 2026 | 8024.5 µg/m³ | 397thof 2,866 | South Korea and Japan, 10 to 15 February 2026 South Korea, February 2026 |
| November 2025 | 7521.8 µg/m³ | 358thof 2,715 | South Korea and Japan, November 2025 South Korea, 5 to 7 November 2025 |
| April 2024 | 7421.5 µg/m³ | 183rdof 2,520 | South Korea, 26 to 27 April 2024 Japan and South Korea, April 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.
Cheonan's worst days
| Day | US AQI | Episode |
|---|---|---|
| 21 Jan 2025 | 16474.5 µg/m³ | Japan and South Korea, 17 to 24 January 2025 |
| 22 Jan 2025 | 15764.0 µg/m³ | Japan and South Korea, 17 to 24 January 2025 |
| 13 Feb 2026 | 15358.5 µg/m³ | South Korea and Japan, 10 to 15 February 2026 |
| 14 Feb 2026 | 15256.7 µg/m³ | South Korea and Japan, 10 to 15 February 2026 |
| 20 Jan 2025 | 15055.2 µg/m³ | Japan and South Korea, 17 to 24 January 2025 |
| 5 Feb 2026 | 14653.8 µg/m³ | South Korea, February 2026 |
| 16 Jan 2026 | 14252.2 µg/m³ | South Korea and Japan, January 2026 |
| 18 Mar 2026 | 14051.3 µg/m³ | South Korea, 15 to 18 March 2026 |
| 10 Mar 2025 | 13950.8 µg/m³ | South Korea, 9 to 11 March 2025 |
| 27 Mar 2026 | 13750.3 µg/m³ | Japan and South Korea, March 2026 |
Daily means, the highest since 23 Mar 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, Cheonan, South Korea, 23 Mar 2024 – 12 Oct 2026. Monitor data from Korea Air Ministry of Environment via OpenAQ; sources listed at smogrank.com/sources. smogrank.com/kr/cheonan/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.
Cheonan 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).