SmogRank / Episodes / United Kingdom
United Kingdom and The Netherlands, March 2024
For 2 days, from 11 to 12 March 2024, 20 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 Dartford, England, United Kingdom: 38.4 µg/m³ on 11 March, about 5.3× its usual 7.3.
No cause named We have no fire or smoke records for these days, so we only say what the measurements show.
Cities reached 20 in 2 countries
Days 2 11 to 12 March 2024
Worst day 11 March 18 cities counted
Furthest above usual 6.2× Biggleswade
Day by day
Play 11 March 18 cities at twice their usual or more
Dunkirk Koksijde Boulogne-sur-Mer Roeselare Maldegem Béthune Izegem Seaford Menen Kortrijk Brighton Roubaix Lens Evergem Gent 's-Gravenzande Douai Tournai Lochristi Maassluis The Hague Reading Spijkenisse Denain Rotterdam Oxford Valenciennes Hillegom Beveren Stabroek Zwijndrecht Ridderkerk Royal Leamington Spa Kapellen Antwerp Willebroek Mons Badhoevedorp Zaanstad Portsmouth Grimbergen Brussels Mechelen Amsterdam Breda Leeds Zaventem Purmerend Andover Middlesbrough Southampton Maarssen Birmingham IJsselstein Medemblik Utrecht Charleroi Aarschot Tilburg Stoke-on-Trent Mol Namur Manchester Newcastle upon Tyne Barneveld Eindhoven Irlam Andenne Houthalen Hasselt Warrington Wigan Nijmegen Bristol Flémalle-Haute Preston Liège Marche-en-Famenne Speke Venray Liverpool Newport Heerlen Venlo Aachen Nettetal Eupen Cardiff Groningen Mönchengladbach Jülich Wesel Krefeld Jüchen Duisburg Bergheim Enschede Borken Düsseldorf Oberhausen Ratingen Bottrop Briton Ferry Essen Newton Abbot Gelsenkirchen Köln Leverkusen Wuppertal Hattingen Lingen Bonn Datteln Barnstaple Dortmund Hagen Münster Schwerte Plymouth Unna Lüdenscheid Saltash Neuwied Friesoythe Bendorf Koblenz Osnabrück Wilhelmshaven Soest Oldenburg Netphen Limburg an der Lahn Velsen-Zuid Velserbroek Grays Hayes London Gillingham Chesterfield Barnsley York Sheffield Bexley Dagenham Canterbury Kingston upon Hull Canvey Island Clacton-on-Sea Dartford Norwich Newmarket Biggleswade 8 Mar 9 10 11 12 13 14 15 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
Bexley Bexley, 8 March: no reading Bexley, 9 March: 26.2 µg/m³, 3.6× usual Bexley, 10 March: 15.1 µg/m³, 2.1× usual Bexley, 11 March: 34.1 µg/m³, 4.7× usual Bexley, 12 March: 25.8 µg/m³, 3.6× usual Bexley, 13 March: 4.8 µg/m³, 0.7× usual Bexley, 14 March: 5.2 µg/m³, 0.7× usual Bexley, 15 March: 5.5 µg/m³, 0.8× usual Dartford Dartford, 8 March: no reading Dartford, 9 March: 15.9 µg/m³, 2.2× usual Dartford, 10 March: 18.8 µg/m³, 2.6× usual Dartford, 11 March: 38.4 µg/m³, 5.3× usual Dartford, 12 March: 12.6 µg/m³, 1.7× usual Dartford, 13 March: 6.3 µg/m³, 0.9× usual Dartford, 14 March: 6.6 µg/m³, 0.9× usual Dartford, 15 March: 8.4 µg/m³, 1.2× usual Grays Grays, 8 March: no reading Grays, 9 March: 12.3 µg/m³, 1.4× usual Grays, 10 March: 16.3 µg/m³, 1.8× usual Grays, 11 March: 35.2 µg/m³, 3.9× usual Grays, 12 March: 12.6 µg/m³, 1.4× usual Grays, 13 March: 5.5 µg/m³, 0.6× usual Grays, 14 March: 9.9 µg/m³, 1.1× usual Grays, 15 March: 7.6 µg/m³, 0.8× usual Norwich Norwich, 8 March: no reading Norwich, 9 March: no reading Norwich, 10 March: no reading Norwich, 11 March: 34.4 µg/m³, 5.5× usual Norwich, 12 March: 20.3 µg/m³, 3.2× usual Norwich, 13 March: 5.4 µg/m³, 0.9× usual Norwich, 14 March: 5.8 µg/m³, 0.9× usual Norwich, 15 March: 5.9 µg/m³, 0.9× usual Canvey Island Canvey Island, 8 March: no reading Canvey Island, 9 March: no reading Canvey Island, 10 March: no reading Canvey Island, 11 March: 34.0 µg/m³, 5.2× usual Canvey Island, 12 March: 28.2 µg/m³, 4.3× usual Canvey Island, 13 March: 5.9 µg/m³, 0.9× usual Canvey Island, 14 March: 4.7 µg/m³, 0.7× usual Canvey Island, 15 March: 5.7 µg/m³, 0.9× usual Kingston upon Hull Kingston upon Hull, 8 March: no reading Kingston upon Hull, 9 March: no reading Kingston upon Hull, 10 March: no reading Kingston upon Hull, 11 March: 33.9 µg/m³, 5.1× usual Kingston upon Hull, 12 March: 22.0 µg/m³, 3.3× usual Kingston upon Hull, 13 March: 5.8 µg/m³, 0.9× usual Kingston upon Hull, 14 March: 5.0 µg/m³, 0.8× usual Kingston upon Hull, 15 March: 5.0 µg/m³, 0.8× usual London London, 8 March: no reading London, 9 March: 13.8 µg/m³, 1.6× usual London, 10 March: 15.6 µg/m³, 1.9× usual London, 11 March: 33.8 µg/m³, 4.0× usual London, 12 March: 9.1 µg/m³, 1.1× usual London, 13 March: 5.2 µg/m³, 0.6× usual London, 14 March: 6.4 µg/m³, 0.8× usual London, 15 March: 7.1 µg/m³, 0.8× usual Newmarket Newmarket, 8 March: no reading Newmarket, 9 March: no reading Newmarket, 10 March: no reading Newmarket, 11 March: 32.7 µg/m³, 6.1× usual Newmarket, 12 March: 21.2 µg/m³, 3.9× usual Newmarket, 13 March: 3.0 µg/m³, 0.6× usual Newmarket, 14 March: 4.7 µg/m³, 0.9× usual Newmarket, 15 March: 4.4 µg/m³, 0.8× usual Biggleswade Biggleswade, 8 March: no reading Biggleswade, 9 March: no reading Biggleswade, 10 March: no reading Biggleswade, 11 March: 31.7 µg/m³, 6.2× usual Biggleswade, 12 March: 22.3 µg/m³, 4.4× usual Biggleswade, 13 March: 4.8 µg/m³, 0.9× usual Biggleswade, 14 March: 6.1 µg/m³, 1.2× usual Biggleswade, 15 March: 6.4 µg/m³, 1.3× usual Clacton-on-Sea Clacton-on-Sea, 8 March: no reading Clacton-on-Sea, 9 March: no reading Clacton-on-Sea, 10 March: no reading Clacton-on-Sea, 11 March: 31.4 µg/m³, 5.3× usual Clacton-on-Sea, 12 March: 23.3 µg/m³, 3.9× usual Clacton-on-Sea, 13 March: 5.6 µg/m³, 0.9× usual Clacton-on-Sea, 14 March: 5.1 µg/m³, 0.9× usual Clacton-on-Sea, 15 March: no reading Canterbury Canterbury, 8 March: no reading Canterbury, 9 March: no reading Canterbury, 10 March: no reading Canterbury, 11 March: 29.3 µg/m³, 5.0× usual Canterbury, 12 March: 27.4 µg/m³, 4.6× usual Canterbury, 13 March: 5.7 µg/m³, 1.0× usual Canterbury, 14 March: 5.9 µg/m³, 1.0× usual Canterbury, 15 March: 6.7 µg/m³, 1.1× usual Sheffield Sheffield, 8 March: no reading Sheffield, 9 March: no reading Sheffield, 10 March: no reading Sheffield, 11 March: 29.0 µg/m³, 4.5× usual Sheffield, 12 March: 19.0 µg/m³, 2.9× usual Sheffield, 13 March: 2.2 µg/m³, 0.3× usual Sheffield, 14 March: 3.6 µg/m³, 0.6× usual Sheffield, 15 March: 4.4 µg/m³, 0.7× usual Barnsley Barnsley, 8 March: no reading Barnsley, 9 March: no reading Barnsley, 10 March: no reading Barnsley, 11 March: 27.3 µg/m³, 4.3× usual Barnsley, 12 March: 18.4 µg/m³, 2.9× usual Barnsley, 13 March: 2.7 µg/m³, 0.4× usual Barnsley, 14 March: no reading Barnsley, 15 March: no reading Dagenham Dagenham, 8 March: no reading Dagenham, 9 March: 7.9 µg/m³, 1.5× usual Dagenham, 10 March: 12.6 µg/m³, 2.4× usual Dagenham, 11 March: 25.7 µg/m³, 4.9× usual Dagenham, 12 March: 7.2 µg/m³, 1.4× usual Dagenham, 13 March: 3.4 µg/m³, 0.7× usual Dagenham, 14 March: 3.1 µg/m³, 0.6× usual Dagenham, 15 March: 5.0 µg/m³, 1.0× usual Chesterfield Chesterfield, 8 March: no reading Chesterfield, 9 March: no reading Chesterfield, 10 March: no reading Chesterfield, 11 March: 25.7 µg/m³, 4.2× usual Chesterfield, 12 March: 17.1 µg/m³, 2.8× usual Chesterfield, 13 March: 2.8 µg/m³, 0.5× usual Chesterfield, 14 March: 4.0 µg/m³, 0.7× usual Chesterfield, 15 March: 3.7 µg/m³, 0.6× usual Gillingham Gillingham, 8 March: no reading Gillingham, 9 March: no reading Gillingham, 10 March: no reading Gillingham, 11 March: 25.6 µg/m³, 4.1× usual Gillingham, 12 March: 23.0 µg/m³, 3.7× usual Gillingham, 13 March: 5.2 µg/m³, 0.8× usual Gillingham, 14 March: 4.3 µg/m³, 0.7× usual Gillingham, 15 March: 5.6 µg/m³, 0.9× usual York York, 8 March: no reading York, 9 March: no reading York, 10 March: no reading York, 11 March: 25.2 µg/m³, 4.3× usual York, 12 March: 19.9 µg/m³, 3.4× usual York, 13 March: 5.8 µg/m³, 1.0× usual York, 14 March: 3.4 µg/m³, 0.6× usual York, 15 March: 4.3 µg/m³, 0.7× usual Hayes Hayes, 8 March: no reading Hayes, 9 March: no reading Hayes, 10 March: no reading Hayes, 11 March: 25.1 µg/m³, 4.0× usual Hayes, 12 March: 20.2 µg/m³, 3.3× usual Hayes, 13 March: 4.0 µg/m³, 0.6× usual Hayes, 14 March: 5.1 µg/m³, 0.8× usual Hayes, 15 March: no reading Velsen-Zuid Velsen-Zuid, 8 March: no reading Velsen-Zuid, 9 March: no reading Velsen-Zuid, 10 March: no reading Velsen-Zuid, 11 March: no reading Velsen-Zuid, 12 March: 27.1 µg/m³, 2.9× usual Velsen-Zuid, 13 March: no reading Velsen-Zuid, 14 March: no reading Velsen-Zuid, 15 March: no reading Velserbroek Velserbroek, 8 March: no reading Velserbroek, 9 March: no reading Velserbroek, 10 March: no reading Velserbroek, 11 March: no reading Velserbroek, 12 March: 25.2 µg/m³, 3.0× usual Velserbroek, 13 March: no reading Velserbroek, 14 March: no reading Velserbroek, 15 March: no reading 8 Mar 9 10 11 12 13 14 15 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. Good 0–50
Moderate 51–100
Sensitive groups 101–150
Unhealthy 151–200
Very unhealthy 201–300
Hazardous 301+
Every city it reached
City Days Highest Usual Above usual
Biggleswade England, United Kingdom 1 11 March 5.1 6.2× Newmarket England, United Kingdom 1 11 March 5.4 6.1× Norwich England, United Kingdom 1 11 March 6.3 5.5× Clacton-on-Sea England, United Kingdom 1 11 March 5.9 5.3× Dartford England, United Kingdom 1 11 March 7.3 5.3× Canvey Island England, United Kingdom 2 11 March 6.5 5.2× Kingston upon Hull England, United Kingdom 1 11 March 6.6 5.1× Canterbury England, United Kingdom 2 11 March 5.9 5.0× Dagenham England, United Kingdom 1 11 March 5.2 4.9× Bexley England, United Kingdom 2 11 March 7.2 4.7× Sheffield England, United Kingdom 1 11 March 6.5 4.5× York England, United Kingdom 1 11 March 5.8 4.3× Barnsley England, United Kingdom 1 11 March 6.4 4.3× Chesterfield England, United Kingdom 1 11 March 6.1 4.2× Gillingham England, United Kingdom 1 11 March 6.2 4.1× Hayes England, United Kingdom 1 11 March 6.2 4.0× London England, United Kingdom 1 11 March 8.4 4.0× Grays England, United Kingdom 1 11 March 9.0 3.9× Velserbroek North Holland, The Netherlands 1 12 March 8.3 3.0× Velsen-Zuid North Holland, The Netherlands 1 12 March 9.5 2.9×
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 4 of 9 episodes in the United Kingdom and The Netherlands since our records began, by cities reached.
France, The Netherlands and United Kingdom, January 2023 66 United Kingdom and Belgium, September 2023 42 Western Europe, November 2024 38 United Kingdom and The Netherlands, March 2024 20 Belgium and United Kingdom, April 2025 16 United Kingdom and The Netherlands, September 2024 13 United Kingdom, Belgium and France, June 2023 10 United Kingdom, May 2025 9 United Kingdom, April 2025 8 Bars: cities reached; colour: the level of the episode's highest daily reading.
Use this page SmogRank, United Kingdom and The Netherlands, March 2024: 20 cities with PM2.5 at twice their usual or more, 11 to 12 March 2024, smogrank.com/episodes/2024-03-united-kingdom-and-the-netherlands (accessed 3 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.
