SmogRank / Senegal / Saint-Louis / Saint-Louis

Saint-Louis, month by month

Saint-Louis has a measured daily mean on 198 days since 13 March 2026. Its worst month was September 2026, at 123 US AQI (44.5 µg/m³), 39th of 2,997 cities on that month's world ranking. Its cleanest was August 2026, at 22 US AQI (4.0 µg/m³).

Every month since 2026

2026too few days for a mean (a year needs 200)198 days measured

JanFebMar19 daysApr59#642 May61#440 Jun55#553 Jul42#1,988 Aug22#2,838 Sep123#39 Oct81#59

Each square is a month's mean PM2.5 in US AQI from Saint-Louis'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-Louis marked; each year, the year's. A dashed square is the running month, so far.

Good0–50

Moderate51–100

Unhealthy for 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

1 month

Month	Why
Mar 2026	19 of 31 days measured; a month needs 22.

A day counts once 18 hours of it are measured; a month needs 70% of its days.

Saint-Louis's worst months

Month	US AQI	Days measured	World rank
September 2026	12344.5 µg/m³	26 of 30	39thof 2,997
May 2026	6114.6 µg/m³	23 of 31	440thof 2,874
April 2026	5913.5 µg/m³	30 of 30	642ndof 2,941
June 2026	5511.1 µg/m³	30 of 30	553rdof 2,497
July 2026	427.6 µg/m³	31 of 31	1,988thof 2,784
August 2026	224.0 µg/m³	29 of 31	2,838thof 2,896

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-Louis's worst days

Day	US AQI
21 Sept 2026	469309.7 µg/m³
17 Sept 2026	314231.9 µg/m³
9 Sept 2026	220145.0 µg/m³
18 Sept 2026	14653.9 µg/m³
23 Sept 2026	13951.0 µg/m³
9 Oct 2026	13449.1 µg/m³
22 Sept 2026	12143.8 µg/m³
28 Sept 2026	11842.3 µg/m³
13 Sept 2026	10838.3 µg/m³
11 Oct 2026	10336.4 µg/m³

Daily means, the highest since 13 Mar 2026; 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-Louis, Senegal, 13 Mar 2026 – 11 Oct 2026. Monitor data from AirGradient via OpenAQ; sources listed at smogrank.com/sources. smogrank.com/sn/saint-louis/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-Louis now: the last 24 hours, its ranks today and the last 12 months day by day.

Updated 2026-10-13 04:07 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).