SmogRank / Bulgaria / Sofia-Capital / Sofia
Sofia, month by month
Sofia has a measured daily mean on 1,074 days since 1 January 2023. Its worst month was January 2024, at 72 US AQI (20.5 µg/m³), 258th of 2,385 cities on that month's world ranking. Its cleanest was May 2024, at 39 US AQI (7.0 µg/m³). 2025 averaged 58 US AQI (12.7 µg/m³), against 56 US AQI (11.8 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
13 months
| Month | Why |
|---|---|
| Jan 2026 | 21 of 31 days measured; a month needs 22. The others: 10 with under 18 hours of readings or readings that failed our checks. |
| Oct 2025 | 18 of 31 days measured; a month needs 22. The others: 13 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. |
| May 2025 | 18 of 31 days measured; a month needs 22. The others: 13 with under 18 hours of readings or readings that failed our checks. |
| Jan 2025 | 20 of 31 days measured; a month needs 22. The others: 11 with under 18 hours of readings or readings that failed our checks. |
| Oct 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. |
| Sep 2024 | No day measured. The others: 30 with under 18 hours of readings or readings that failed our checks. |
| Aug 2024 | 8 of 31 days measured; a month needs 22. The others: 23 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. |
| Apr 2023 | 19 of 30 days measured; a month needs 21. The others: 2 missing from OpenAQ's archive, 9 with under 18 hours of readings or readings that failed our checks. |
| Mar 2023 | 9 of 31 days measured; a month needs 22. The others: 20 missing from OpenAQ's archive, 2 with under 18 hours of readings or readings that failed our checks. |
| Feb 2023 | 3 of 28 days measured; a month needs 20. The others: 25 missing from OpenAQ's archive. |
| Jan 2023 | 17 of 31 days measured; a month needs 22. The others: 7 missing from OpenAQ's archive, 7 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.
Sofia's worst months
| Month | US AQI | World rank | Episode |
|---|---|---|---|
| January 2024 | 7220.5 µg/m³ | 258thof 2,385 | Europe, 8 to 27 January 2024 South-eastern Europe, 28 December 2023 to 1 January 2024 |
| December 2025 | 6516.6 µg/m³ | 662ndof 3,006 | North Macedonia, Bulgaria and 2 more countries, December 2025 Eastern Europe, 16 to 21 December 2025 |
| March 2026 | 6315.5 µg/m³ | 801stof 2,971 | – |
| February 2025 | 6315.3 µg/m³ | 850thof 2,633 | Europe, 14 February to 1 March 2025 |
| February 2026 | 6013.9 µg/m³ | 863rdof 2,866 | – |
| September 2023 | 5913.6 µg/m³ | 233rdof 2,176 | – |
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.
Sofia's worst days
| Day | US AQI | Episode |
|---|---|---|
| 1 Jan 2023 | 15865.3 µg/m³ | Eastern Europe, January 2023 |
| 15 Jan 2024 | 15459.3 µg/m³ | Europe, 8 to 27 January 2024 |
| 8 Oct 2025 | 15055.4 µg/m³ | – |
| 7 Jan 2025 | 14352.5 µg/m³ | Eastern Europe, January 2025 |
| 22 Jan 2024 | 13850.6 µg/m³ | Europe, 8 to 27 January 2024 |
| 23 Jan 2024 | 13649.9 µg/m³ | Europe, 8 to 27 January 2024 |
| 6 Jan 2024 | 12846.4 µg/m³ | – |
| 19 Dec 2025 | 12043.4 µg/m³ | Eastern Europe, 16 to 21 December 2025 |
| 18 Dec 2025 | 11942.7 µg/m³ | Eastern Europe, 16 to 21 December 2025 |
| 14 Jan 2024 | 11741.9 µg/m³ | Europe, 8 to 27 January 2024 |
Daily means, the highest since 1 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, Sofia, Bulgaria, 1 Jan 2023 – 11 Oct 2026. Monitor data from EEA, via OpenAQ and from the publisher directly; sources listed at smogrank.com/sources. smogrank.com/bg/sofia/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.
Sofia 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).