SmogRank / Finland / North Ostrobothnia / Oulu

Oulu, month by month

Oulu has a measured daily mean on 1,016 days since 12 January 2023. Its worst month was July 2025, at 37 US AQI (6.6 µg/m³), 2,104th of 2,889 cities on that month's world ranking. Its cleanest was November 2024, at 16 US AQI (2.9 µg/m³). 2025 averaged 25 US AQI (4.5 µg/m³), against 25 US AQI (4.5 µg/m³) in 2024.

Every month since 2023

202623 so far266 days measured2,736th of 2,791 in the world
Jan28#2,321Feb28#2,604Mar21#2,834Apr24#2,656May20#2,729Jun22#2,317Jul23#2,693Aug24#2,811Sep18#2,880Oct20#2,576
202525 for the year290 days measured2,594th of 2,681 in the world
Jan21 daysFeb34#2,067Mar21 daysApr23#2,737May25#2,464Jun20 daysJul37#2,104Aug19#2,850Sep25#2,806Oct18#2,554Nov18#2,650Dec19 days
202425 for the year265 days measured2,005th of 2,097 in the world
Jan27#2,096Feb31#1,956Mar15 daysApr21#2,272May29#2,202Jun25#2,312Jul26#2,346Aug15 daysSepnoneOct14 daysNov16#2,579Dec19#2,524
2023too few days for a mean (a year needs 256)195 days measured
Jan5 daysFeb31#1,046Mar19 daysApr3 daysMaynoneJunnoneJul1 dayAug21 daysSep23#2,086Oct24#1,886Nov17#2,194Dec29#1,987
Each square is a month's mean PM2.5 in US AQI from Oulu'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 Oulu 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

15 months
MonthWhy
Dec 202519 of 31 days measured; a month needs 22. The others: 12 with under 18 hours of readings or readings that failed our checks.
Jun 202520 of 30 days measured; a month needs 21. The others: 10 with under 18 hours of readings or readings that failed our checks.
Mar 202521 of 31 days measured; a month needs 22. The others: 10 with under 18 hours of readings or readings that failed our checks.
Jan 202521 of 31 days measured; a month needs 22. The others: 10 with under 18 hours of readings or readings that failed our checks.
Oct 202414 of 31 days measured; a month needs 22. The others: 17 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 202415 of 31 days measured; a month needs 22. The others: 16 with under 18 hours of readings or readings that failed our checks.
Mar 202415 of 31 days measured; a month needs 22. The others: 16 with under 18 hours of readings or readings that failed our checks.
Aug 202321 of 31 days measured; a month needs 22. The others: 10 with under 18 hours of readings or readings that failed our checks.
Jul 20231 of 31 days measured; a month needs 22. The others: 30 with under 18 hours of readings or readings that failed our checks.
Jun 2023No day measured. The others: 30 with under 18 hours of readings or readings that failed our checks.
May 2023No day measured. The others: 31 with under 18 hours of readings or readings that failed our checks.
Apr 20233 of 30 days measured; a month needs 21. The others: 27 with under 18 hours of readings or readings that failed our checks.
Mar 202319 of 31 days measured; a month needs 22. The others: 1 missing from OpenAQ's archive, 11 with under 18 hours of readings or readings that failed our checks.
Jan 20235 of 31 days measured; a month needs 22. The others: 1 missing from OpenAQ's archive, 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.

Oulu's worst months

MonthUS AQIDays measuredWorld rank
July 2025 376.6 µg/m³30 of 312,104thof 2,889
February 2025 346.2 µg/m³21 of 282,067thof 2,633
February 2024 315.6 µg/m³28 of 291,956thof 2,486
February 2023 315.5 µg/m³25 of 281,046thof 1,129
May 2024 295.3 µg/m³31 of 312,202ndof 2,684
December 2023 295.2 µg/m³31 of 311,987thof 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.

Oulu's worst days

DayUS AQI
22 Feb 2023 6516.6 µg/m³
10 Feb 2024 6416.0 µg/m³
21 Feb 2023 6315.4 µg/m³
23 Aug 2026 6315.3 µg/m³
20 Jul 2025 6013.9 µg/m³
12 Feb 2024 6013.7 µg/m³
23 Feb 2025 6013.7 µg/m³
7 Mar 2023 5913.5 µg/m³
11 Feb 2024 5913.4 µg/m³
24 Aug 2026 5813.0 µg/m³

Daily means, the highest since 12 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, Oulu, Finland, 12 Jan 2023 – 11 Oct 2026. Monitor data from EEA, via OpenAQ and from the publisher directly; sources listed at smogrank.com/sources. smogrank.com/fi/oulu/history (accessed 12 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.

Oulu 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).