SmogRank / Germany / North Rhine-Westphalia / Bielefeld
Bielefeld, month by month
Bielefeld has a measured daily mean on 1,068 days since 11 January 2023. Its worst month was February 2025, at 75 US AQI (22.0 µg/m³), 413th of 2,633 cities on that month's world ranking. Its cleanest was October 2025, at 29 US AQI (5.3 µg/m³). 2025 averaged 52 US AQI (9.8 µg/m³), against 48 US AQI (8.7 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.
Bielefeld's worst months
| Month | US AQI | World rank | Episode |
|---|---|---|---|
| February 2025 | 7522.0 µg/m³ | 413thof 2,633 | Europe, 1 to 14 February 2025 |
| January 2026 | 6818.2 µg/m³ | 558thof 2,617 | Europe, January and February 2026 Europe, December 2025 to January 2026 |
| March 2025 | 6717.7 µg/m³ | 709thof 2,862 | Europe, March 2025 Germany, Poland and 25 more countries, March 2025 |
| February 2023 | 6214.9 µg/m³ | 350thof 1,129 | Europe, 6 to 25 February 2023 |
| February 2026 | 6114.5 µg/m³ | 808thof 2,866 | Europe, January and February 2026 |
| March 2026 | 6014.1 µg/m³ | 933rdof 2,971 | Europe, 1 to 12 March 2026 |
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.
Bielefeld's worst days
| Day | US AQI | Episode |
|---|---|---|
| 13 Feb 2025 | 15357.9 µg/m³ | Europe, 1 to 14 February 2025 |
| 24 Jan 2026 | 15256.6 µg/m³ | Europe, January and February 2026 |
| 25 Jan 2026 | 14453.0 µg/m³ | Europe, January and February 2026 |
| 10 Feb 2025 | 13348.4 µg/m³ | Europe, 1 to 14 February 2025 |
| 10 Mar 2025 | 13047.3 µg/m³ | Germany, Poland and 25 more countries, March 2025 |
| 9 Feb 2025 | 11340.2 µg/m³ | Europe, 1 to 14 February 2025 |
| 9 Mar 2025 | 11340.2 µg/m³ | Germany, Poland and 25 more countries, March 2025 |
| 5 Feb 2026 | 10938.7 µg/m³ | Europe, January and February 2026 |
| 23 Jan 2026 | 10637.7 µg/m³ | Europe, January and February 2026 |
| 11 Mar 2025 | 10436.7 µg/m³ | Germany, Poland and 25 more countries, March 2025 |
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, Bielefeld, 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/bielefeld/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.
Bielefeld 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).