SmogRank / Sweden / Halland / Onsala

Onsala, month by month

Onsala has a measured daily mean on 334 days since 1 January 2023. Its worst month was September 2023, at 54 US AQI (10.6 µg/m³), 491st of 2,176 cities on that month's world ranking. Its cleanest was November 2023, at 22 US AQI (3.9 µg/m³).

Every month since 2023

2026too few days for a mean (a year needs 199)0 days measured
JannoneFebnoneMarnoneAprnoneMaynoneJunnoneJulnoneAugnoneSepnoneOctnone
2025too few days for a mean (a year needs 256)0 days measured
JannoneFebnoneMarnoneAprnoneMaynoneJunnoneJulnoneAugnoneSepnoneOctnoneNovnoneDecnone
2024too few days for a mean (a year needs 257)69 days measured
Jan33#1,850Feb23#2,301Mar10 daysAprnoneMaynoneJunnoneJulnoneAugnoneSepnoneOctnoneNovnoneDecnone
202338 for the year265 days measured1,078th of 1,355 in the world
Jan19 daysFeb3 daysMar6 daysApr32#1,241May37#1,203Jun46#1,060Jul36#1,028Aug43#1,101Sep54#491Oct24#1,886Nov22#2,134Dec19 days
Each square is a month's mean PM2.5 in US AQI from Onsala'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 Onsala marked; each year, the year's.
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

36 months
MonthWhy
Oct 2026No day measured.
Sep 2026No day measured.
Aug 2026No day measured.
Jul 2026No day measured.
Jun 2026No day measured.
May 2026No day measured.
Apr 2026No day measured.
Mar 2026No day measured.
Feb 2026No day measured.
Jan 2026No day measured.
Dec 2025No day measured.
Nov 2025No day measured.
Oct 2025No day measured.
Sep 2025No day measured.
Aug 2025No day measured.
Jul 2025No day measured.
Jun 2025No day measured.
May 2025No day measured.
Apr 2025No day measured.
Mar 2025No day measured.
Feb 2025No day measured.
Jan 2025No day measured.
Dec 2024No day measured. The others: 31 with no readings from the monitor.
Nov 2024No day measured. The others: 30 with no readings from the monitor.
Oct 2024No day measured. The others: 31 with no readings from the monitor.
Sep 2024No day measured. The others: 30 with no readings from the monitor.
Aug 2024No day measured. The others: 31 with no readings from the monitor.
Jul 2024No day measured. The others: 31 with no readings from the monitor.
Jun 2024No day measured. The others: 30 with no readings from the monitor.
May 2024No day measured. The others: 31 with no readings from the monitor.
Apr 2024No day measured. The others: 30 with no readings from the monitor.
Mar 202410 of 31 days measured; a month needs 22. The others: 20 with no readings from the monitor, 1 with readings for part of the day (a day needs 18 hours).
Dec 202319 of 31 days measured; a month needs 22. The others: 12 with readings for part of the day (a day needs 18 hours).
Mar 20236 of 31 days measured; a month needs 22. The others: 3 with no readings from the monitor, 2 with readings for part of the day (a day needs 18 hours), 20 missing from OpenAQ's archive.
Feb 20233 of 28 days measured; a month needs 20. The others: 25 missing from OpenAQ's archive.
Jan 202319 of 31 days measured; a month needs 22. The others: 3 with no readings from the monitor, 3 with readings for part of the day (a day needs 18 hours), 6 missing from OpenAQ's archive.

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

Onsala's worst months

MonthUS AQIDays measuredWorld rank
September 2023 5410.6 µg/m³28 of 30491stof 2,176
June 2023 468.3 µg/m³27 of 301,060thof 1,603
August 2023 437.7 µg/m³27 of 311,101stof 1,980
May 2023 376.6 µg/m³31 of 311,203rdof 1,600
July 2023 366.5 µg/m³28 of 311,028thof 1,432
January 2024 335.9 µg/m³31 of 311,850thof 2,385

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.

Onsala's worst days

DayUS AQI
10 Sept 2023 7823.5 µg/m³
27 Sept 2023 7723.3 µg/m³
11 Sept 2023 7321.1 µg/m³
3 Mar 2024 6919.0 µg/m³
15 Feb 2023 6818.1 µg/m³
9 Sept 2023 6717.8 µg/m³
28 Sept 2023 6717.6 µg/m³
19 Mar 2023 6617.2 µg/m³
20 Jun 2023 6617.0 µg/m³
19 Jun 2023 6516.6 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, Onsala, Sweden, 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/se/onsala/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.

Onsala 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).