SmogRank / Spain / Madrid / Alcalá de Henares
Alcalá de Henares, month by month
Alcalá de Henares has a measured daily mean on 911 days since 1 January 2023. Its worst month was August 2025, at 62 US AQI (15.1 µg/m³), 346th of 2,901 cities on that month's world ranking. Its cleanest was January 2026, at 31 US AQI (5.5 µg/m³). 2025 averaged 50 US AQI (9.0 µg/m³), against 54 US AQI (10.7 µg/m³) in 2023.
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
14 months
| Month | Why |
|---|---|
| Oct 2026 | 7 of 12 days measured; a month needs 9. The others: 2 with no readings from the monitors, 3 with readings for part of the day (a day needs 18 hours). |
| Jul 2026 | 5 of 31 days measured; a month needs 22. The others: 26 with under 18 hours of readings or readings that failed our checks. |
| Jun 2026 | No day measured. The others: 30 with under 18 hours of readings or readings that failed our checks. |
| May 2026 | No day measured. The others: 31 with under 18 hours of readings or readings that failed our checks. |
| Apr 2026 | No day measured. The others: 30 with under 18 hours of readings or readings that failed our checks. |
| Mar 2026 | No day measured. The others: 31 with under 18 hours of readings or readings that failed our checks. |
| Feb 2026 | 8 of 28 days measured; a month needs 20. The others: 20 with under 18 hours of readings or readings that failed our checks. |
| Oct 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. |
| Sep 2024 | No day measured. The others: 30 with under 18 hours of readings or readings that failed our checks. |
| Aug 2024 | 1 of 31 days measured; a month needs 22. The others: 30 with under 18 hours of readings or readings that failed our checks. |
| Jul 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. |
| May 2024 | 2 of 31 days measured; a month needs 22. The others: 29 with under 18 hours of readings or readings that failed our checks. |
| Apr 2024 | 11 of 30 days measured; a month needs 21. The others: 19 with under 18 hours of readings or readings that failed our checks. |
| Mar 2024 | 10 of 31 days measured; a month needs 22. The others: 21 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.
Alcalá de Henares's worst months
| Month | US AQI | World rank | Episode |
|---|---|---|---|
| August 2025 | 6215.1 µg/m³ | 346thof 2,901 | Northern Spain, August 2025 Spain, Portugal and Andorra, August 2025 |
| July 2023 | 6114.2 µg/m³ | 190thof 1,432 | Andalusia, Madrid and Castille-La Mancha, Spain, July 2023 |
| August 2023 | 5913.6 µg/m³ | 244thof 1,980 | Madrid, Castille and León and Castille-La Mancha, Spain, August 2023 |
| June 2025 | 5712.3 µg/m³ | 756thof 2,508 | – |
| February 2023 | 5612.0 µg/m³ | 539thof 1,129 | Spain, France and Portugal, February 2023 |
| December 2024 | 5611.9 µg/m³ | 681stof 2,616 | – |
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.
Alcalá de Henares's worst days
| Day | US AQI | Episode |
|---|---|---|
| 31 Oct 2024 | 13147.8 µg/m³ | Northern Spain, October 2024 |
| 9 Aug 2026 | 12444.8 µg/m³ | – |
| 30 Oct 2024 | 10336.4 µg/m³ | Northern Spain, October 2024 |
| 9 Aug 2023 | 10135.6 µg/m³ | Madrid, Castille and León and Castille-La Mancha, Spain, August 2023 |
| 22 Feb 2023 | 9331.5 µg/m³ | Spain, France and Portugal, February 2023 |
| 10 Apr 2023 | 8728.3 µg/m³ | Madrid, Andalusia and Castille-La Mancha, Spain, April 2023 |
| 7 Apr 2024 | 8527.2 µg/m³ | Spain, April 2024 |
| 27 Aug 2025 | 8326.2 µg/m³ | Northern Spain, August 2025 |
| 19 Jul 2023 | 8226.0 µg/m³ | Andalusia, Madrid and Castille-La Mancha, Spain, July 2023 |
| 20 Aug 2025 | 8125.2 µg/m³ | Spain, Portugal and Andorra, August 2025 |
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, Alcalá de Henares, Spain, 1 Jan 2023 – 9 Oct 2026. Monitor data from EEA, via OpenAQ and from the publisher directly; sources listed at smogrank.com/sources. smogrank.com/es/alcala-de-henares/history (accessed 13 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.
Alcalá de Henares now: the last 24 hours, its ranks today and the last 12 months day by day.
Updated 2026-10-13 03:07 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).