SmogRank / Romania / Cluj County / Dej
Dej, month by month
Dej has a measured daily mean on 793 days since 22 November 2023. Its worst month was January 2026, at 170 US AQI (82.3 µg/m³), 20th of 2,617 cities on that month's world ranking. Its cleanest was May 2024, at 35 US AQI (6.3 µg/m³).
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
10 months
| Month | Why |
|---|---|
| Oct 2026 | 7 of 11 days measured; a month needs 8. The others: 4 with readings for part of the day (a day needs 18 hours). |
| Aug 2026 | 20 of 31 days measured; a month needs 22. The others: 11 with under 18 hours of readings or readings that failed our checks. |
| Jun 2026 | 14 of 30 days measured; a month needs 21. The others: 16 with under 18 hours of readings or readings that failed our checks. |
| Nov 2025 | 15 of 30 days measured; a month needs 21. The others: 15 with under 18 hours of readings or readings that failed our checks. |
| Jun 2025 | 19 of 30 days measured; a month needs 21. The others: 11 with under 18 hours of readings or readings that failed our checks. |
| Oct 2024 | 11 of 31 days measured; a month needs 22. The others: 20 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 | 14 of 31 days measured; a month needs 22. The others: 17 with under 18 hours of readings or readings that failed our checks. |
| Mar 2024 | 13 of 31 days measured; a month needs 22. The others: 18 with under 18 hours of readings or readings that failed our checks. |
| Nov 2023 | 9 of 30 days measured; a month needs 21. |
A day counts once 18 hours of it are measured; a month needs 70% of its days.
Dej's worst months
| Month | US AQI | World rank | Episode |
|---|---|---|---|
| January 2026 | 17082.3 µg/m³ | 20thof 2,617 | Europe, January and February 2026 |
| February 2025 | 14352.6 µg/m³ | 39thof 2,633 | – |
| January 2025 | 12746.1 µg/m³ | 40thof 2,474 | Europe, 24 December 2024 to 3 January 2025 |
| February 2024 | 12143.5 µg/m³ | 48thof 2,486 | – |
| December 2024 | 11641.7 µg/m³ | 37thof 2,616 | Europe, 24 December 2024 to 3 January 2025 Serbia, Slovenia and 10 more countries, December 2024 |
| November 2024 | 11641.6 µg/m³ | 41stof 2,624 | Europe, November 2024 Eastern Europe, October and November 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.
Dej's worst days
| Day | US AQI | Episode |
|---|---|---|
| 22 Jan 2026 | 242167.0 µg/m³ | Europe, January and February 2026 |
| 21 Jan 2026 | 237162.0 µg/m³ | Europe, January and February 2026 |
| 20 Jan 2026 | 227152.0 µg/m³ | Europe, January and February 2026 |
| 23 Jan 2026 | 211135.5 µg/m³ | Europe, January and February 2026 |
| 18 Jan 2026 | 202126.5 µg/m³ | Europe, January and February 2026 |
| 24 Jan 2026 | 193116.0 µg/m³ | Europe, January and February 2026 |
| 25 Jan 2026 | 18198.1 µg/m³ | Europe, January and February 2026 |
| 30 Jan 2026 | 17995.1 µg/m³ | Europe, January and February 2026 |
| 11 Mar 2025 | 17690.9 µg/m³ | Germany, Poland and 25 more countries, March 2025 Romania, Hungary and Serbia, March 2025 |
| 28 Dec 2024 | 17590.2 µg/m³ | Europe, 24 December 2024 to 3 January 2025 |
Daily means, the highest since 22 Nov 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, Dej, Romania, 22 Nov 2023 – 10 Oct 2026. Monitor data from EEA, via OpenAQ and from the publisher directly; sources listed at smogrank.com/sources. smogrank.com/ro/dej/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.
Dej 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).