SmogRank / Episodes / United Kingdom
United Kingdom and The Netherlands, September 2024
For 2 days, from 19 to 20 September 2024, 13 cities in the United Kingdom, The Netherlands and Jersey had PM2.5 at least twice their usual for the time of year. The worst reading was Canterbury, England, United Kingdom: 33.1 µg/m³ on 20 September, about 5.0× its usual 6.6.
No cause named We have no fire or smoke records for these days, so we only say what the measurements show.
Cities reached 13 in 3 countries
Days 2 19 to 20 September 2024
Worst day 20 September 9 cities counted
Furthest above usual 6.1× Saint Helier
Day by day
Play 20 September 9 cities at twice their usual or more
Gillingham Grays Dartford Dagenham London Newmarket Norwich Hayes Biggleswade Reading Southampton Oxford Royal Leamington Spa Hillegom Tilburg IJsselstein Birmingham Utrecht Eindhoven Bristol Medemblik Stoke-on-Trent Barneveld Heerlen Nijmegen Newport Venray Cardiff Newton Abbot Briton Ferry Barnstaple Plymouth Enschede Saltash Bexley Brighton Breda Portsmouth Canvey Island The Hague Rotterdam Maarssen Andover Seaford Canterbury Clacton-on-Sea Saint Helier 16 Sep 17 18 19 20 21 22 23 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
Saint Helier Saint Helier, 16 September: 4.1 µg/m³, 0.8× usual Saint Helier, 17 September: 2.9 µg/m³, 0.6× usual Saint Helier, 18 September: 17.7 µg/m³, 3.5× usual Saint Helier, 19 September: 28.7 µg/m³, 5.7× usual Saint Helier, 20 September: 30.7 µg/m³, 6.1× usual Saint Helier, 21 September: 12.7 µg/m³, 2.5× usual Saint Helier, 22 September: 14.1 µg/m³, 2.8× usual Saint Helier, 23 September: no reading Maarssen Maarssen, 16 September: 10.4 µg/m³, 1.8× usual Maarssen, 17 September: 5.9 µg/m³, 1.0× usual Maarssen, 18 September: 17.5 µg/m³, 3.1× usual Maarssen, 19 September: 27.7 µg/m³, 4.9× usual Maarssen, 20 September: 22.5 µg/m³, 3.9× usual Maarssen, 21 September: 17.3 µg/m³, 3.0× usual Maarssen, 22 September: 16.6 µg/m³, 2.9× usual Maarssen, 23 September: 10.8 µg/m³, 1.9× usual The Hague The Hague, 16 September: 7.4 µg/m³, 1.3× usual The Hague, 17 September: 5.9 µg/m³, 1.0× usual The Hague, 18 September: 16.0 µg/m³, 2.8× usual The Hague, 19 September: 27.5 µg/m³, 4.7× usual The Hague, 20 September: 21.9 µg/m³, 3.8× usual The Hague, 21 September: 20.9 µg/m³, 3.6× usual The Hague, 22 September: 17.3 µg/m³, 3.0× usual The Hague, 23 September: 9.4 µg/m³, 1.6× usual Rotterdam Rotterdam, 16 September: 5.7 µg/m³, 1.0× usual Rotterdam, 17 September: 3.2 µg/m³, 0.6× usual Rotterdam, 18 September: 14.2 µg/m³, 2.6× usual Rotterdam, 19 September: 26.4 µg/m³, 4.8× usual Rotterdam, 20 September: 17.0 µg/m³, 3.1× usual Rotterdam, 21 September: 16.8 µg/m³, 3.1× usual Rotterdam, 22 September: 16.4 µg/m³, 3.0× usual Rotterdam, 23 September: 4.9 µg/m³, 0.9× usual Breda Breda, 16 September: 11.0 µg/m³, 2.0× usual Breda, 17 September: 5.1 µg/m³, 0.9× usual Breda, 18 September: 19.6 µg/m³, 3.5× usual Breda, 19 September: 25.4 µg/m³, 4.5× usual Breda, 20 September: 18.0 µg/m³, 3.2× usual Breda, 21 September: 19.1 µg/m³, 3.4× usual Breda, 22 September: 17.5 µg/m³, 3.1× usual Breda, 23 September: 7.0 µg/m³, 1.3× usual Canterbury Canterbury, 16 September: 4.9 µg/m³, 0.7× usual Canterbury, 17 September: 3.9 µg/m³, 0.6× usual Canterbury, 18 September: 8.6 µg/m³, 1.3× usual Canterbury, 19 September: 25.1 µg/m³, 3.8× usual Canterbury, 20 September: 33.1 µg/m³, 5.0× usual Canterbury, 21 September: 24.0 µg/m³, 3.6× usual Canterbury, 22 September: 25.8 µg/m³, 3.9× usual Canterbury, 23 September: 10.0 µg/m³, 1.5× usual Canvey Island Canvey Island, 16 September: 4.7 µg/m³, 0.8× usual Canvey Island, 17 September: 4.4 µg/m³, 0.7× usual Canvey Island, 18 September: 7.3 µg/m³, 1.2× usual Canvey Island, 19 September: 19.2 µg/m³, 3.3× usual Canvey Island, 20 September: 28.0 µg/m³, 4.7× usual Canvey Island, 21 September: 23.1 µg/m³, 3.9× usual Canvey Island, 22 September: 24.9 µg/m³, 4.2× usual Canvey Island, 23 September: 9.0 µg/m³, 1.5× usual Clacton-on-Sea Clacton-on-Sea, 16 September: 4.6 µg/m³, 0.9× usual Clacton-on-Sea, 17 September: 3.3 µg/m³, 0.6× usual Clacton-on-Sea, 18 September: 5.5 µg/m³, 1.1× usual Clacton-on-Sea, 19 September: 17.9 µg/m³, 3.4× usual Clacton-on-Sea, 20 September: 27.0 µg/m³, 5.2× usual Clacton-on-Sea, 21 September: 22.4 µg/m³, 4.3× usual Clacton-on-Sea, 22 September: 22.9 µg/m³, 4.4× usual Clacton-on-Sea, 23 September: 11.0 µg/m³, 2.1× usual Portsmouth Portsmouth, 16 September: 4.2 µg/m³, 0.7× usual Portsmouth, 17 September: no reading Portsmouth, 18 September: 7.0 µg/m³, 1.2× usual Portsmouth, 19 September: 19.7 µg/m³, 3.5× usual Portsmouth, 20 September: 26.1 µg/m³, 4.6× usual Portsmouth, 21 September: 21.3 µg/m³, 3.7× usual Portsmouth, 22 September: 9.8 µg/m³, 1.7× usual Portsmouth, 23 September: 8.3 µg/m³, 1.5× usual Seaford Seaford, 16 September: 3.6 µg/m³, 0.7× usual Seaford, 17 September: 3.2 µg/m³, 0.6× usual Seaford, 18 September: 6.4 µg/m³, 1.2× usual Seaford, 19 September: 20.7 µg/m³, 4.0× usual Seaford, 20 September: 26.0 µg/m³, 5.0× usual Seaford, 21 September: 18.1 µg/m³, 3.5× usual Seaford, 22 September: 9.0 µg/m³, 1.7× usual Seaford, 23 September: 7.5 µg/m³, 1.4× usual Bexley Bexley, 16 September: 4.4 µg/m³, 0.7× usual Bexley, 17 September: 3.4 µg/m³, 0.6× usual Bexley, 18 September: 6.0 µg/m³, 1.0× usual Bexley, 19 September: 18.7 µg/m³, 3.1× usual Bexley, 20 September: 26.0 µg/m³, 4.3× usual Bexley, 21 September: 22.1 µg/m³, 3.7× usual Bexley, 22 September: 21.3 µg/m³, 3.6× usual Bexley, 23 September: 9.8 µg/m³, 1.6× usual Brighton Brighton, 16 September: 3.5 µg/m³, 0.6× usual Brighton, 17 September: 3.3 µg/m³, 0.6× usual Brighton, 18 September: 6.8 µg/m³, 1.2× usual Brighton, 19 September: 20.4 µg/m³, 3.6× usual Brighton, 20 September: 25.7 µg/m³, 4.5× usual Brighton, 21 September: 18.8 µg/m³, 3.3× usual Brighton, 22 September: 8.1 µg/m³, 1.4× usual Brighton, 23 September: 8.3 µg/m³, 1.5× usual Andover Andover, 16 September: 4.6 µg/m³, 0.9× usual Andover, 17 September: 3.8 µg/m³, 0.8× usual Andover, 18 September: 5.6 µg/m³, 1.1× usual Andover, 19 September: 16.2 µg/m³, 3.2× usual Andover, 20 September: 25.2 µg/m³, 5.0× usual Andover, 21 September: 19.8 µg/m³, 4.0× usual Andover, 22 September: 12.0 µg/m³, 2.4× usual Andover, 23 September: 7.9 µg/m³, 1.6× usual 16 Sep 17 18 19 20 21 22 23 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
Saint Helier St Helier, Jersey 2 20 September 2.5 6.1× Clacton-on-Sea England, United Kingdom 1 20 September 5.2 5.2× Andover England, United Kingdom 1 20 September 4.7 5.0× Canterbury England, United Kingdom 2 20 September 6.6 5.0× Seaford England, United Kingdom 1 20 September 5.2 5.0× Maarssen Utrecht, The Netherlands 1 19 September 5.7 4.9× Rotterdam South Holland, The Netherlands 1 19 September 5.5 4.8× Canvey Island England, United Kingdom 1 20 September 5.9 4.7× The Hague South Holland, The Netherlands 1 19 September 5.8 4.7× Portsmouth England, United Kingdom 1 20 September 5.7 4.6× Breda North Brabant, The Netherlands 1 19 September 5.6 4.5× Brighton England, United Kingdom 1 20 September 5.7 4.5× Bexley England, United Kingdom 1 20 September 6.0 4.3×
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 6 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, September 2024: 13 cities with PM2.5 at twice their usual or more, 19 to 20 September 2024, smogrank.com/episodes/2024-09-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.
