SmogRank / Reunion / Reunion / Saint-Denis

Saint-Denis, month by month

Saint-Denis has a measured daily mean on 752 days since 11 January 2023. Its worst month was February 2023, at 35 US AQI (6.3 µg/m³), 992nd of 1,129 cities on that month's world ranking. Its cleanest was September 2026, at 18 US AQI (3.2 µg/m³).

Every month since 2023

202621 so far212 days measured2,769th of 2,798 in the world
Jan11 daysFeb23#2,700Mar23#2,800Apr21#2,765May19#2,760Jun16 daysJul18#2,743Aug20#2,864Sep18#2,905Oct18#2,672
2025too few days for a mean (a year needs 256)176 days measured
Jan2 daysFeb13 daysMar19 daysApr13 daysMay11 daysJun6 daysJul21 daysAug13 daysSep31#2,285Oct13 daysNov20 daysDec22#2,855
2024too few days for a mean (a year needs 257)41 days measured
JannoneFebnoneMarnoneAprnoneMaynoneJunnoneJulnoneAug8 daysSepnoneOct3 daysNov10 daysDec20 days
202325 for the year323 days measured1,295th of 1,355 in the world
Jan7 daysFeb35#992Mar19 daysApr21#1,500May21#1,540Jun23#1,483Jul26#1,280Aug22#1,924Sep28#1,982Oct31#1,615Nov22#2,134Dec19#2,179
Each square is a month's mean PM2.5 in US AQI from Saint-Denis's measured days, with its place on that month's world ranking under it. A month has a mean once 70% of its days are measured, the rule the monthly rankings use; under that, the square gives the days measured. Each square opens that month's ranking with Saint-Denis marked; each year, the year's. A dashed square is the running month, so far.
Good0–50
Moderate51–100
Sensitive groups101–150
Unhealthy151–200
Very unhealthy201–300
Hazardous301+

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

26 months
MonthWhy
Jun 202616 of 30 days measured; a month needs 21. The others: 14 with under 18 hours of readings or readings that failed our checks.
Jan 202611 of 31 days measured; a month needs 22. The others: 20 with under 18 hours of readings or readings that failed our checks.
Nov 202520 of 30 days measured; a month needs 21. The others: 10 with under 18 hours of readings or readings that failed our checks.
Oct 202513 of 31 days measured; a month needs 22. The others: 18 with under 18 hours of readings or readings that failed our checks.
Aug 202513 of 31 days measured; a month needs 22. The others: 18 with under 18 hours of readings or readings that failed our checks.
Jul 202521 of 31 days measured; a month needs 22. The others: 10 with under 18 hours of readings or readings that failed our checks.
Jun 20256 of 30 days measured; a month needs 21. The others: 24 with under 18 hours of readings or readings that failed our checks.
May 202511 of 31 days measured; a month needs 22. The others: 20 with under 18 hours of readings or readings that failed our checks.
Apr 202513 of 30 days measured; a month needs 21. The others: 17 with under 18 hours of readings or readings that failed our checks.
Mar 202519 of 31 days measured; a month needs 22. The others: 12 with under 18 hours of readings or readings that failed our checks.
Feb 202513 of 28 days measured; a month needs 20. The others: 15 with under 18 hours of readings or readings that failed our checks.
Jan 20252 of 31 days measured; a month needs 22. The others: 29 with under 18 hours of readings or readings that failed our checks.
Dec 202420 of 31 days measured; a month needs 22. The others: 11 with under 18 hours of readings or readings that failed our checks.
Nov 202410 of 30 days measured; a month needs 21. The others: 20 with under 18 hours of readings or readings that failed our checks.
Oct 20243 of 31 days measured; a month needs 22. The others: 28 with under 18 hours of readings or readings that failed our checks.
Sep 2024No day measured. The others: 30 with under 18 hours of readings or readings that failed our checks.
Aug 20248 of 31 days measured; a month needs 22. The others: 23 with under 18 hours of readings or readings that failed our checks.
Jul 2024No day measured. The others: 31 with under 18 hours of readings or readings that failed our checks.
Jun 2024No day measured. The others: 30 with under 18 hours of readings or readings that failed our checks.
May 2024No day measured. The others: 31 with under 18 hours of readings or readings that failed our checks.
Apr 2024No day measured. The others: 30 with under 18 hours of readings or readings that failed our checks.
Mar 2024No day measured. The others: 31 with under 18 hours of readings or readings that failed our checks.
Feb 2024No day measured. The others: 1 missing from OpenAQ's archive, 28 with under 18 hours of readings or readings that failed our checks.
Jan 2024No day measured. The others: 31 with under 18 hours of readings or readings that failed our checks.
Mar 202319 of 31 days measured; a month needs 22. The others: 10 missing from OpenAQ's archive, 2 with under 18 hours of readings or readings that failed our checks.
Jan 20237 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.

Saint-Denis's worst months

MonthUS AQIDays measuredWorld rank
February 2023 356.3 µg/m³28 of 28992ndof 1,129
October 2023 315.6 µg/m³30 of 311,615thof 2,012
September 2025 315.6 µg/m³23 of 302,285thof 3,104
September 2023 285.0 µg/m³30 of 301,982ndof 2,176
July 2023 264.6 µg/m³29 of 311,280thof 1,432
June 2023 234.2 µg/m³30 of 301,483rdof 1,603

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.

Saint-Denis's worst days

DayUS AQI
16 Oct 2023 5410.9 µg/m³
19 Oct 2023 529.9 µg/m³
21 Oct 2023 529.6 µg/m³
26 Oct 2023 498.9 µg/m³
4 Sept 2025 498.8 µg/m³
1 Feb 2023 488.7 µg/m³
27 Oct 2023 488.7 µg/m³
22 Feb 2023 488.6 µg/m³
21 Sept 2025 488.6 µg/m³
19 Sept 2023 478.5 µg/m³

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, Saint-Denis, Reunion, 11 Jan 2023 – 12 Oct 2026. Monitor data from EEA, via OpenAQ and from the publisher directly; sources listed at smogrank.com/sources. smogrank.com/re/saint-denis/history (accessed 13 Oct 2026).

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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.

Saint-Denis now: the last 24 hours, its ranks today and the last 12 months day by day.

Updated 2026-10-13 01:07 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).