SmogRank / France / Auvergne-Rhône-Alpes / Crolles
Crolles, month by month
Crolles has a measured daily mean on 1,009 days since 1 January 2023. Its worst month was February 2025, at 72 US AQI (20.2 µg/m³), 557th of 2,633 cities on that month's world ranking. Its cleanest was September 2025, at 22 US AQI (3.9 µg/m³). 2025 averaged 52 US AQI (9.8 µg/m³), against 52 US AQI (9.4 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
15 months
| Month | Why |
|---|---|
| Jun 2026 | 18 of 30 days measured; a month needs 21. The others: 12 with under 18 hours of readings or readings that failed our checks. |
| 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 | 19 of 31 days measured; a month needs 22. The others: 12 with under 18 hours of readings or readings that failed our checks. |
| Aug 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. |
| Jun 2025 | 17 of 30 days measured; a month needs 21. The others: 13 with under 18 hours of readings or readings that failed our checks. |
| May 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 | 15 of 31 days measured; a month needs 22. The others: 16 with under 18 hours of readings or readings that failed our checks. |
| Jun 2024 | No day measured. The others: 30 with under 18 hours of readings or readings that failed our checks. |
| May 2024 | No day measured. The others: 31 with under 18 hours of readings or readings that failed our checks. |
| Apr 2024 | 2 of 30 days measured; a month needs 21. The others: 28 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. |
| Mar 2023 | 11 of 31 days measured; a month needs 22. The others: 20 missing from OpenAQ's archive. |
| Feb 2023 | 3 of 28 days measured; a month needs 20. The others: 25 missing from OpenAQ's archive. |
A day counts once 18 hours of it are measured; a month needs 70% of its days.
Crolles's worst months
| Month | US AQI | World rank | Episode |
|---|---|---|---|
| February 2025 | 7220.2 µg/m³ | 557thof 2,633 | Europe, 14 February to 1 March 2025 Europe, 1 to 14 February 2025 |
| January 2023 | 7120.0 µg/m³ | 154thof 1,261 | Auvergne-Rhône-Alpes and Provence-Alpes-Côte d'Azur, France, January 2023 France and Monaco, January 2023 |
| December 2025 | 7119.9 µg/m³ | 507thof 3,006 | – |
| January 2024 | 6717.6 µg/m³ | 350thof 2,385 | Western Europe, January 2024 |
| December 2024 | 6516.6 µg/m³ | 396thof 2,616 | – |
| December 2023 | 6516.4 µg/m³ | 246thof 2,247 | – |
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.
Crolles's worst days
| Day | US AQI | Episode |
|---|---|---|
| 20 Jan 2025 | 12444.7 µg/m³ | Germany, France and 19 more countries, January 2025 |
| 11 Jun 2025 | 11842.3 µg/m³ | Europe, June 2025 |
| 19 Jan 2025 | 11039.2 µg/m³ | Germany, France and 19 more countries, January 2025 |
| 18 Jan 2026 | 11039.1 µg/m³ | Europe, January and February 2026 |
| 28 Jan 2023 | 10637.5 µg/m³ | – |
| 14 Jan 2024 | 10537.3 µg/m³ | Western Europe, January 2024 |
| 15 Jan 2024 | 10236.1 µg/m³ | Western Europe, January 2024 |
| 30 Dec 2025 | 10236.0 µg/m³ | – |
| 25 Jan 2023 | 10235.9 µg/m³ | France and Monaco, January 2023 |
| 28 Dec 2023 | 10235.9 µg/m³ | – |
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, Crolles, France, 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/fr/crolles/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.
Crolles 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).