SmogRank / Germany / North Rhine-Westphalia / Köln
Köln, month by month
Köln has a measured daily mean on 1,072 days since 11 January 2023. Its worst month was February 2025, at 72 US AQI (20.5 µg/m³), 531st of 2,633 cities on that month's world ranking. Its cleanest was August 2026, at 33 US AQI (5.9 µg/m³). 2025 averaged 52 US AQI (9.8 µg/m³), against 49 US AQI (8.9 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
12 months
| Month | Why |
|---|---|
| Sep 2026 | 17 of 30 days measured; a month needs 21. The others: 13 with readings for part of the day (a day needs 18 hours). |
| Jun 2026 | 19 of 30 days measured; a month needs 21. The others: 11 with under 18 hours of readings or readings that failed our checks. |
| Jun 2025 | 18 of 30 days measured; a month needs 21. The others: 12 with under 18 hours of readings or readings that failed our checks. |
| Oct 2024 | 15 of 31 days measured; a month needs 22. The others: 16 with under 18 hours of readings or readings that failed our checks. |
| Sep 2024 | No day measured. The others: 30 with under 18 hours of readings or readings that failed our checks. |
| Aug 2024 | 15 of 31 days measured; a month needs 22. The others: 16 with under 18 hours of readings or readings that failed our checks. |
| Mar 2024 | 15 of 31 days measured; a month needs 22. The others: 16 with under 18 hours of readings or readings that failed our checks. |
| Oct 2023 | 8 of 31 days measured; a month needs 22. The others: 23 with under 18 hours of readings or readings that failed our checks. |
| Sep 2023 | No day measured. The others: 30 with under 18 hours of readings or readings that failed our checks. |
| Aug 2023 | No day measured. The others: 31 with under 18 hours of readings or readings that failed our checks. |
| Jul 2023 | 14 of 31 days measured; a month needs 22. The others: 17 with under 18 hours of readings or readings that failed our checks. |
| Jan 2023 | 7 of 31 days measured; a month needs 22. The others: 14 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.
Köln's worst months
| Month | US AQI | World rank | Episode |
|---|---|---|---|
| February 2025 | 7220.5 µg/m³ | 531stof 2,633 | Europe, 14 February to 1 March 2025 Europe, 1 to 14 February 2025 |
| January 2026 | 6416.3 µg/m³ | 675thof 2,617 | Europe, January and February 2026 Europe, December 2025 to January 2026 |
| March 2025 | 6315.6 µg/m³ | 893rdof 2,862 | Europe, March 2025 Germany, Poland and 25 more countries, March 2025and 1 more |
| February 2023 | 6114.7 µg/m³ | 368thof 1,129 | Europe, 28 February to 4 March 2023 Europe, 6 to 25 February 2023 |
| March 2026 | 5812.6 µg/m³ | 1,114thof 2,971 | Europe, 18 to 25 March 2026 Europe, 1 to 12 March 2026 |
| January 2024 | 5712.2 µg/m³ | 678thof 2,385 | Europe, 8 to 27 January 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.
Köln's worst days
| Day | US AQI | Episode |
|---|---|---|
| 25 Mar 2025 | 14352.6 µg/m³ | Europe, March 2025 |
| 13 Feb 2025 | 14051.4 µg/m³ | Europe, 1 to 14 February 2025 |
| 10 Feb 2025 | 12344.3 µg/m³ | Europe, 1 to 14 February 2025 |
| 26 Jan 2026 | 12143.7 µg/m³ | Europe, January and February 2026 |
| 25 Jan 2026 | 11541.3 µg/m³ | Europe, January and February 2026 |
| 11 Mar 2025 | 11440.6 µg/m³ | Germany, Poland and 25 more countries, March 2025 |
| 11 Jan 2024 | 10838.4 µg/m³ | Europe, 8 to 27 January 2024 |
| 14 Feb 2025 | 10738.1 µg/m³ | Europe, 14 February to 1 March 2025 Europe, 1 to 14 February 2025 |
| 9 Feb 2025 | 10035.3 µg/m³ | Europe, 1 to 14 February 2025 |
| 3 Mar 2023 | 9633.0 µg/m³ | Europe, 28 February to 4 March 2023 |
Daily means, the highest since 11 Jan 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, Köln, Germany, 11 Jan 2023 – 10 Oct 2026. Monitor data from EEA, via OpenAQ and from the publisher directly; sources listed at smogrank.com/sources. smogrank.com/de/koeln/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.
Köln now: the last 24 hours, its ranks today and the last 12 months day by day.
Updated 2026-10-12 17:07 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).