SmogRank / United Kingdom / England / Hoo

Hoo, month by month

Hoo has a measured daily mean on 782 days since 1 January 2023. Its worst month was September 2023, at 63 US AQI (15.4 µg/m³), 168th of 2,176 cities on that month's world ranking. Its cleanest was July 2024, at 25 US AQI (4.5 µg/m³).

Every month since 2023

2026too few days for a mean (a year needs 199)87 days measured
Jan48#1,337Feb41#2,138Mar20 daysAprnoneMaynoneJunnoneJulnoneAugnoneSepnoneOct24#2,386
2025too few days for a mean (a year needs 256)230 days measured
JannoneFebnoneMar2 daysApr59#633May52#1,004Jun40#1,983Jul34#2,236Aug41#2,059Sep28#2,552Oct38#1,211Nov9 daysDec44#1,837
2024too few days for a mean (a year needs 257)250 days measured
Jan51#972Feb28#2,131Mar21 daysApr18 daysMay54#624Jun20 daysJul25#2,368Aug36#1,654Sep51#578Oct36#1,303NovnoneDecnone
2023too few days for a mean (a year needs 256)215 days measured
Jan20 daysFeb3 daysMar11 daysApr19 daysMay18 daysJun16 daysJul18 daysAug21 daysSep63#168Oct15 daysNov41#1,320Dec42#1,368
Each square is a month's mean PM2.5 in US AQI from Hoo'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 Hoo 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

25 months
MonthWhy
Sep 2026No day measured. The others: 30 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 2026No day measured. The others: 31 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.
Mar 202620 of 31 days measured; a month needs 22. The others: 11 with under 18 hours of readings or readings that failed our checks.
Nov 20259 of 30 days measured; a month needs 21. The others: 21 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.
Jun 202420 of 30 days measured; a month needs 21. The others: 10 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.
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 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.
Apr 202319 of 30 days measured; a month needs 21. The others: 2 missing from OpenAQ's archive, 9 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.
Jan 202320 of 31 days measured; a month needs 22. The others: 7 missing from OpenAQ's archive, 4 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.

Hoo's worst months

MonthUS AQIDays measuredWorld rankEpisode
September 2023 6315.4 µg/m³23 of 30168thof 2,176United Kingdom, Belgium and 2 more countries, September 2023
April 2025 5913.4 µg/m³28 of 30633rdof 2,951United Kingdom, Belgium and 2 more countries, April 2025
United Kingdom and France, April 2025
May 2024 5410.8 µg/m³30 of 31624thof 2,684–
May 2025 529.4 µg/m³29 of 311,004thof 2,826United Kingdom and The Netherlands, May 2025
January 2024 519.3 µg/m³30 of 31972ndof 2,385–
September 2024 519.1 µg/m³26 of 30578thof 2,010United Kingdom, The Netherlands and Jersey, September 2024

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.

Hoo's worst days

DayUS AQIEpisode
10 Sept 2023 14453.0 µg/m³United Kingdom, Belgium and 2 more countries, September 2023
15 Feb 2023 13247.9 µg/m³Europe, 6 to 25 February 2023
14 Feb 2023 11942.8 µg/m³Europe, 6 to 25 February 2023
8 Sept 2023 10938.7 µg/m³United Kingdom, Belgium and 2 more countries, September 2023
9 Mar 2026 10336.3 µg/m³Europe, 1 to 12 March 2026
7 Sept 2023 10236.1 µg/m³United Kingdom, Belgium and 2 more countries, September 2023
11 Mar 2024 9734.0 µg/m³United Kingdom and The Netherlands, March 2024
4 Apr 2025 9633.0 µg/m³United Kingdom and France, April 2025
2 May 2025 9432.2 µg/m³United Kingdom and The Netherlands, May 2025
12 Apr 2025 9130.5 µg/m³United Kingdom, Belgium and 2 more countries, April 2025

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, Hoo, United Kingdom, 1 Jan 2023 – 11 Oct 2026. Monitor data from UK-AIR (Defra), read from the publisher; sources listed at smogrank.com/sources. smogrank.com/gb/hoo/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.

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

Updated 2026-10-12 21:07 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).