SmogRank / United Kingdom / England / Portsmouth

Portsmouth, month by month

Portsmouth has a measured daily mean on 787 days since 1 January 2023. Its worst month was March 2026, at 57 US AQI (12.2 µg/m³), 1,175th of 2,971 cities on that month's world ranking. Its cleanest was August 2023, at 26 US AQI (4.7 µg/m³).

Every month since 2023

2026too few days for a mean (a year needs 200)96 days measured
Jan39#1,817Feb33#2,427Mar57#1,175AprnoneMay3 daysJunnoneJulnoneAugnoneSep1 dayOct28#2,145
2025too few days for a mean (a year needs 256)227 days measured
JannoneFebnoneMar2 daysApr54#1,009May46#1,255Jun35#2,128Jul31#2,486Aug34#2,450Sep28#2,600Oct21 daysNov10 daysDec42#1,959
2024too few days for a mean (a year needs 257)240 days measured
Jan52#907Feb38#1,499Mar21 daysApr18 daysMay50#995Jun36#1,877Jul31#2,097Aug18 daysSep20 daysOct34#1,409NovnoneDecnone
2023too few days for a mean (a year needs 256)224 days measured
Jan54#434Feb3 daysMar11 daysApr53#396May18 daysJun16 daysJul18 daysAug26#1,852Sep47#937Oct15 daysNov37#1,514Dec44#1,260
Each square is a month's mean PM2.5 in US AQI from Portsmouth'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 Portsmouth 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

23 months
MonthWhy
Sep 20261 of 30 days measured; a month needs 21. The others: 29 with under 18 hours of readings or readings that failed our checks.
Aug 2026No day measured. The others: 31 with under 18 hours of readings or readings that failed our checks.
Jul 2026No day measured. The others: 31 with under 18 hours of readings or readings that failed our checks.
Jun 2026No day measured. The others: 30 with under 18 hours of readings or readings that failed our checks.
May 20263 of 31 days measured; a month needs 22. The others: 28 with under 18 hours of readings or readings that failed our checks.
Apr 2026No day measured. The others: 30 with under 18 hours of readings or readings that failed our checks.
Nov 202510 of 30 days measured; a month needs 21. The others: 20 with under 18 hours of readings or readings that failed our checks.
Oct 202521 of 31 days measured; a month needs 22. The others: 10 with under 18 hours of readings or readings that failed our checks.
Mar 20252 of 31 days measured; a month needs 22. The others: 29 with under 18 hours of readings or readings that failed our checks.
Feb 2025No day measured. The others: 28 with under 18 hours of readings or readings that failed our checks.
Jan 2025No day measured. The others: 31 with under 18 hours of readings or readings that failed our checks.
Dec 2024No day measured. The others: 31 with under 18 hours of readings or readings that failed our checks.
Nov 2024No day measured. The others: 30 with under 18 hours of readings or readings that failed our checks.
Sep 202420 of 30 days measured; a month needs 21. The others: 10 with under 18 hours of readings or readings that failed our checks.
Aug 202418 of 31 days measured; a month needs 22. The others: 13 with under 18 hours of readings or readings that failed our checks.
Apr 202418 of 30 days measured; a month needs 21. The others: 12 with under 18 hours of readings or readings that failed our checks.
Mar 202421 of 31 days measured; a month needs 22. The others: 10 with under 18 hours of readings or readings that failed our checks.
Oct 202315 of 31 days measured; a month needs 22. The others: 16 with under 18 hours of readings or readings that failed our checks.
Jul 202318 of 31 days measured; a month needs 22. The others: 1 missing from OpenAQ's archive, 12 with under 18 hours of readings or readings that failed our checks.
Jun 202316 of 30 days measured; a month needs 21. The others: 14 with under 18 hours of readings or readings that failed our checks.
May 202318 of 31 days measured; a month needs 22. The others: 13 with under 18 hours of readings or readings that failed our checks.
Mar 202311 of 31 days measured; a month needs 22. The others: 20 missing from OpenAQ's archive.
Feb 20233 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.

Portsmouth's worst months

MonthUS AQIDays measuredWorld rankEpisode
March 2026 5712.2 µg/m³25 of 311,175thof 2,971Europe, 1 to 12 March 2026
April 2025 5410.7 µg/m³28 of 301,009thof 2,951–
January 2023 5410.5 µg/m³24 of 31434thof 1,261–
April 2023 5310.4 µg/m³21 of 30396thof 1,622–
January 2024 529.8 µg/m³29 of 31907thof 2,385–
May 2024 509.0 µg/m³29 of 31995thof 2,684–

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.

Portsmouth's worst days

DayUS AQIEpisode
15 Feb 2023 10838.4 µg/m³Europe, 6 to 25 February 2023
9 Mar 2026 10637.4 µg/m³Europe, 1 to 12 March 2026
14 Feb 2023 9633.4 µg/m³Europe, 6 to 25 February 2023
20 Sept 2024 8326.1 µg/m³United Kingdom, The Netherlands and Jersey, September 2024
19 Aug 2024 8225.6 µg/m³–
2 May 2025 8225.6 µg/m³United Kingdom and The Netherlands, May 2025
18 Jun 2023 8024.8 µg/m³–
30 Apr 2023 7823.4 µg/m³–
24 Mar 2026 7823.4 µg/m³–
25 Jan 2023 7622.4 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, Portsmouth, United Kingdom, 1 Jan 2023 – 11 Oct 2026. Monitor data from London Air Quality Network and UK-AIR (Defra), via OpenAQ and from the publisher directly; sources listed at smogrank.com/sources. smogrank.com/gb/portsmouth/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.

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

Updated 2026-10-12 22:07 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).