SmogRank / Episodes / United Kingdom

United Kingdom, May 2025

For 2 days, from 1 to 2 May 2025, 9 cities in the United Kingdom and The Netherlands had PM2.5 at least twice their usual for the time of year. The worst reading was Clacton-on-Sea, England, United Kingdom: 38.1 µg/m³ on 2 May, about 4.9× its usual 7.8.

No cause namedWe have no fire or smoke records for these days, so we only say what the measurements show.
Cities reached9in 2 countries
Days21 to 2 May 2025
Worst day1 May7 cities counted
Furthest above usual4.9×Clacton-on-Sea

Day by day

1 May 7 cities at twice their usual or more
NorwichNewmarketCalaisBoulogne-sur-MerLutonHayesSeafordDunkirkBrightonKoksijdeNorthamptonReadingKingston upon HullDieppeBéthuneLeicesterScunthorpeOxfordRoeselareNottinghamMenenIzegemAmiensRoubaixKortrijkMaldegemRoyal Leamington SpaDoncasterDouaiDerbyAndoverChesterfieldSouthamptonTournaiEvergemSheffieldYorkGentBarnsleyDenainLochristiBirminghamValenciennes's-GravenzandeLeedsCannockSaint-QuentinHigh PeakMaassluisThe HagueSpijkenisseBeverenMonsSchiedamWestburyStoke-on-TrentZwijndrechtStabroekRotterdamAntwerpWillebroekKapellenCheadle HulmeGrimbergenBrusselsHillegomRidderkerkManchesterMechelenVelsen-ZuidVelserbroekZaventemBristolBadhoevedorpRixensartIrlamBredaZaanstadCharleroiAmsterdamWarringtonPurmerendAarschotWiganMaarssenIJsselsteinUtrechtTilburgNewportPrestonNamurMolAndenneHasseltHouthalenEindhovenBarneveldFlémalle-HauteMarche-en-FamenneLiègeNijmegenBriton FerryNewton AbbotVenrayHeerlenVenloEupenAachenBarnstapleJülichMönchengladbachPlymouthJüchenKrefeldSaltashWeselGroningenDuisburgDüsseldorfBorkenOberhausenEnschedeRatingenPulheimBottropEssenKölnLeverkusenTrierGelsenkirchenWuppertalHattingenBonnEmdenLingenDattelnDortmundHagenSchwerteMünsterNeuwiedLüdenscheidUnnaBendorfKoblenzLiverpoolSpekeLondonPortsmouthCanvey IslandMedemblikBexleyGillinghamClacton-on-Sea
28 Apr29301 May2345
Every measured city in the area, coloured by its PM2.5 that day; a dark ring marks a city at twice its usual or more. Bars: cities counted each day, coloured by their median level. Choose a day or press play; without JavaScript, the days link to that day's world ranking.

How it spread

GillinghamGillingham, 28 April: 8.6 µg/m³, 1.3× usualGillingham, 29 April: 11.3 µg/m³, 1.7× usualGillingham, 30 April: 17.0 µg/m³, 2.5× usualGillingham, 1 May: 29.7 µg/m³, 4.4× usualGillingham, 2 May: no readingGillingham, 3 May: 9.5 µg/m³, 1.4× usualGillingham, 4 May: 4.4 µg/m³, 0.6× usualGillingham, 5 May: 3.9 µg/m³, 0.6× usualCanvey IslandCanvey Island, 28 April: 13.4 µg/m³, 1.5× usualCanvey Island, 29 April: 21.3 µg/m³, 2.3× usualCanvey Island, 30 April: 17.5 µg/m³, 1.9× usualCanvey Island, 1 May: 29.6 µg/m³, 3.3× usualCanvey Island, 2 May: 32.2 µg/m³, 3.5× usualCanvey Island, 3 May: 12.1 µg/m³, 1.3× usualCanvey Island, 4 May: 5.7 µg/m³, 0.6× usualCanvey Island, 5 May: no readingBexleyBexley, 28 April: 14.2 µg/m³, 1.8× usualBexley, 29 April: 17.0 µg/m³, 2.2× usualBexley, 30 April: 17.6 µg/m³, 2.3× usualBexley, 1 May: 28.4 µg/m³, 3.7× usualBexley, 2 May: 25.4 µg/m³, 3.3× usualBexley, 3 May: 15.5 µg/m³, 2.0× usualBexley, 4 May: 6.8 µg/m³, 0.9× usualBexley, 5 May: 4.8 µg/m³, 0.6× usualLondonLondon, 28 April: 13.7 µg/m³, 1.6× usualLondon, 29 April: 17.5 µg/m³, 2.1× usualLondon, 30 April: 20.4 µg/m³, 2.4× usualLondon, 1 May: 27.4 µg/m³, 3.3× usualLondon, 2 May: 15.9 µg/m³, 1.9× usualLondon, 3 May: 12.9 µg/m³, 1.5× usualLondon, 4 May: 5.6 µg/m³, 0.7× usualLondon, 5 May: 5.6 µg/m³, 0.7× usualSpekeSpeke, 28 April: 6.2 µg/m³, 0.7× usualSpeke, 29 April: 9.9 µg/m³, 1.1× usualSpeke, 30 April: 16.3 µg/m³, 1.9× usualSpeke, 1 May: 27.4 µg/m³, 3.1× usualSpeke, 2 May: 10.6 µg/m³, 1.2× usualSpeke, 3 May: 7.0 µg/m³, 0.8× usualSpeke, 4 May: 6.5 µg/m³, 0.7× usualSpeke, 5 May: 5.6 µg/m³, 0.6× usualClacton-on-SeaClacton-on-Sea, 28 April: 14.5 µg/m³, 1.9× usualClacton-on-Sea, 29 April: 19.7 µg/m³, 2.5× usualClacton-on-Sea, 30 April: 13.6 µg/m³, 1.7× usualClacton-on-Sea, 1 May: 25.8 µg/m³, 3.3× usualClacton-on-Sea, 2 May: 38.1 µg/m³, 4.9× usualClacton-on-Sea, 3 May: 13.1 µg/m³, 1.7× usualClacton-on-Sea, 4 May: 4.4 µg/m³, 0.6× usualClacton-on-Sea, 5 May: 3.7 µg/m³, 0.5× usualLiverpoolLiverpool, 28 April: 4.0 µg/m³, 0.5× usualLiverpool, 29 April: 8.9 µg/m³, 1.1× usualLiverpool, 30 April: 18.5 µg/m³, 2.3× usualLiverpool, 1 May: 25.5 µg/m³, 3.1× usualLiverpool, 2 May: 10.2 µg/m³, 1.2× usualLiverpool, 3 May: 5.9 µg/m³, 0.7× usualLiverpool, 4 May: 4.3 µg/m³, 0.5× usualLiverpool, 5 May: 3.5 µg/m³, 0.4× usualMedemblikMedemblik, 28 April: 9.8 µg/m³, 1.3× usualMedemblik, 29 April: 10.7 µg/m³, 1.5× usualMedemblik, 30 April: 4.5 µg/m³, 0.6× usualMedemblik, 1 May: 8.5 µg/m³, 1.2× usualMedemblik, 2 May: 27.1 µg/m³, 3.7× usualMedemblik, 3 May: 4.4 µg/m³, 0.6× usualMedemblik, 4 May: 3.6 µg/m³, 0.5× usualMedemblik, 5 May: 5.0 µg/m³, 0.7× usualPortsmouthPortsmouth, 28 April: 15.6 µg/m³, 2.1× usualPortsmouth, 29 April: 11.3 µg/m³, 1.5× usualPortsmouth, 30 April: 15.1 µg/m³, 2.0× usualPortsmouth, 1 May: 18.0 µg/m³, 2.4× usualPortsmouth, 2 May: 25.6 µg/m³, 3.4× usualPortsmouth, 3 May: 13.4 µg/m³, 1.8× usualPortsmouth, 4 May: 6.0 µg/m³, 0.8× usualPortsmouth, 5 May: no reading28 Apr29301 May2345
Every counted city, in the order the episode reached them, 3 days before to 3 after. Each square is a day, coloured by that day's PM2.5; outlined: at twice the city's usual or more.
Good0–50
Moderate51–100
Sensitive groups101–150
Unhealthy151–200
Very unhealthy201–300
Hazardous301+

Every city it reached

CityDaysHighestUsualAbove usual
Clacton-on-SeaEngland, United Kingdom2 38.12 May7.84.9×
GillinghamEngland, United Kingdom1 29.71 May6.84.4×
MedemblikNorth Holland, The Netherlands1 27.12 May7.33.7×
BexleyEngland, United Kingdom2 28.41 May7.73.7×
Canvey IslandEngland, United Kingdom2 32.22 May9.13.5×
PortsmouthEngland, United Kingdom1 25.62 May7.63.4×
LondonEngland, United Kingdom1 27.41 May8.43.3×
SpekeEngland, United Kingdom1 27.41 May8.83.1×
LiverpoolEngland, United Kingdom1 25.51 May8.23.1×

Daily means in µg/m³. Usual: the city's median for this time of year (its days within 21 days of the date, every year, leaving out the week around it). Above usual: its highest day against that.

Against other episodes in the United Kingdom and The Netherlands

Number 5 of 6 episodes in the United Kingdom and The Netherlands since our records began, by cities reached.

Bars: cities reached; colour: the level of the episode's highest daily reading.

Use this page

SmogRank, United Kingdom, May 2025: 9 cities with PM2.5 at twice their usual or more, 1 to 2 May 2025, smogrank.com/episodes/2025-05-united-kingdom (accessed 2 October 2026).

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You're welcome to reuse a single chart, image or figure with this citation and a link. Terms.

An episode is a run of days when many cities close to each other (four or more within 350 km on a day, 8 or more in all) each had a daily PM2.5 mean of at least 25 µg/m³ and at least 2 times their usual for that time of year. Found in our own measurements, not picked by hand. How we find episodes. Values are each city's daily mean of its own monitors; causes are the usual kinds for a pattern like this, not a confirmed source.