SmogRank / Episodes / Poland
Poland, April 2026
For 3 days, from 10 to 12 April 2026, 32 cities in Poland, Czechia and Slovakia had PM2.5 at least twice their usual for the time of year. The worst reading was Radomsko, Łódź Voivodeship, Poland: 60.2 µg/m³ on 11 April, about 4.2× its usual 14.2.
No cause named We have no fire or smoke records for these days, so we only say what the measurements show.
Cities reached 32 in 3 countries
Days 3 10 to 12 April 2026
Worst day 11 April 27 cities counted
Furthest above usual 4.2× Radomsko
Day by day
Play 11 April 27 cities at twice their usual or more
Łódź Katowice Włocławek Bielsko-Biala Płock Kraków Žilina Żyrardów Púchov Kielce Martin Ružomberok Trenčín Liptovský Mikuláš Pruszków Ciechanów Warsaw Konstancin-Jeziorna Židenice Hodonín Jelenia Góra Brno Wawer Poprad Hradec Králové Pardubice Jasło Bardejov Znojmo Prešov Nisko Eisenhüttenstadt Vranov nad Topľou Lublin Frankfurt (Oder) Humenné Cottbus Prague Snina Szczecin Przemyśl Schwedt (Oder) Lubnjow České Budějovice Zamość Strausberg Neuenhagen Königs Wusterhausen Białystok Bernau bei Berlin Blankenfelde-Mahlow Berlin Teltow Luckenwalde Kleinmachnow Oranienburg Potsdam Falkensee Neubrandenburg Nauen Wittenberg Neuruppin Brandenburg an der Havel Altenburg Bitterfeld-Wolfen Dessau Greiz Zeitz Gera Merseburg Halle (Saale) Marktredwitz Weiden Schwandorf in Bayern Legionowo Toruń Radom Bydgoszcz Łask Čadca Jarosław Starachowice Racibórz Poznań Żywiec Jastrzębie Zdrój Wrocław Zielona Góra Zgierz Dębica Rzeszów Mielec Kędzierzyn-Koźle Opole Krosno Czechowice-Dziedzice Gorzów Wielkopolski Kalisz Stodůlky Tarnów Kłodzko Żary Otwock Říčany Brzeg Radomsko 7 Apr 8 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
Jastrzębie Zdrój Jastrzębie Zdrój, 7 April: 8.3 µg/m³, 0.5× usual Jastrzębie Zdrój, 8 April: 11.7 µg/m³, 0.6× usual Jastrzębie Zdrój, 9 April: no reading Jastrzębie Zdrój, 10 April: 42.9 µg/m³, 2.3× usual Jastrzębie Zdrój, 11 April: 39.9 µg/m³, 2.2× usual Jastrzębie Zdrój, 12 April: 35.3 µg/m³, 1.9× usual Jastrzębie Zdrój, 13 April: 15.7 µg/m³, 0.9× usual Jastrzębie Zdrój, 14 April: no reading Jastrzębie Zdrój, 15 April: no reading Czechowice-Dziedzice Czechowice-Dziedzice, 7 April: 6.0 µg/m³, 0.4× usual Czechowice-Dziedzice, 8 April: 11.0 µg/m³, 0.7× usual Czechowice-Dziedzice, 9 April: no reading Czechowice-Dziedzice, 10 April: 42.8 µg/m³, 2.9× usual Czechowice-Dziedzice, 11 April: 39.2 µg/m³, 2.6× usual Czechowice-Dziedzice, 12 April: 31.9 µg/m³, 2.1× usual Czechowice-Dziedzice, 13 April: 11.2 µg/m³, 0.7× usual Czechowice-Dziedzice, 14 April: no reading Czechowice-Dziedzice, 15 April: no reading Tarnów Tarnów, 7 April: 5.4 µg/m³, 0.5× usual Tarnów, 8 April: 5.2 µg/m³, 0.4× usual Tarnów, 9 April: 13.1 µg/m³, 1.1× usual Tarnów, 10 April: 30.7 µg/m³, 2.6× usual Tarnów, 11 April: 37.8 µg/m³, 3.2× usual Tarnów, 12 April: 33.1 µg/m³, 2.8× usual Tarnów, 13 April: 11.8 µg/m³, 1.0× usual Tarnów, 14 April: no reading Tarnów, 15 April: no reading Brzeg Brzeg, 7 April: 5.1 µg/m³, 0.5× usual Brzeg, 8 April: 7.8 µg/m³, 0.8× usual Brzeg, 9 April: no reading Brzeg, 10 April: 28.7 µg/m³, 3.0× usual Brzeg, 11 April: 30.4 µg/m³, 3.2× usual Brzeg, 12 April: 37.8 µg/m³, 3.9× usual Brzeg, 13 April: 14.4 µg/m³, 1.5× usual Brzeg, 14 April: no reading Brzeg, 15 April: no reading Opole Opole, 7 April: 4.2 µg/m³, 0.4× usual Opole, 8 April: 5.7 µg/m³, 0.5× usual Opole, 9 April: 13.9 µg/m³, 1.2× usual Opole, 10 April: 27.7 µg/m³, 2.4× usual Opole, 11 April: 28.3 µg/m³, 2.5× usual Opole, 12 April: 29.5 µg/m³, 2.6× usual Opole, 13 April: 9.1 µg/m³, 0.8× usual Opole, 14 April: no reading Opole, 15 April: no reading Říčany Říčany, 7 April: 1.0 µg/m³, 0.1× usual Říčany, 8 April: 5.7 µg/m³, 0.5× usual Říčany, 9 April: 8.2 µg/m³, 0.7× usual Říčany, 10 April: 26.7 µg/m³, 2.3× usual Říčany, 11 April: 36.2 µg/m³, 3.1× usual Říčany, 12 April: 42.4 µg/m³, 3.6× usual Říčany, 13 April: 25.4 µg/m³, 2.2× usual Říčany, 14 April: 25.4 µg/m³, 2.2× usual Říčany, 15 April: 36.8 µg/m³, 3.1× usual Kędzierzyn-Koźle Kędzierzyn-Koźle, 7 April: 5.0 µg/m³, 0.4× usual Kędzierzyn-Koźle, 8 April: 6.7 µg/m³, 0.6× usual Kędzierzyn-Koźle, 9 April: no reading Kędzierzyn-Koźle, 10 April: 26.4 µg/m³, 2.3× usual Kędzierzyn-Koźle, 11 April: 30.6 µg/m³, 2.6× usual Kędzierzyn-Koźle, 12 April: 29.6 µg/m³, 2.5× usual Kędzierzyn-Koźle, 13 April: 9.6 µg/m³, 0.8× usual Kędzierzyn-Koźle, 14 April: no reading Kędzierzyn-Koźle, 15 April: no reading Radomsko Radomsko, 7 April: 8.6 µg/m³, 0.6× usual Radomsko, 8 April: 15.6 µg/m³, 1.1× usual Radomsko, 9 April: no reading Radomsko, 10 April: 26.4 µg/m³, 1.9× usual Radomsko, 11 April: 60.2 µg/m³, 4.2× usual Radomsko, 12 April: 45.6 µg/m³, 3.2× usual Radomsko, 13 April: 9.8 µg/m³, 0.7× usual Radomsko, 14 April: no reading Radomsko, 15 April: no reading Otwock Otwock, 7 April: 8.9 µg/m³, 0.6× usual Otwock, 8 April: 10.5 µg/m³, 0.7× usual Otwock, 9 April: no reading Otwock, 10 April: 26.4 µg/m³, 1.7× usual Otwock, 11 April: 52.9 µg/m³, 3.5× usual Otwock, 12 April: 48.4 µg/m³, 3.2× usual Otwock, 13 April: 11.4 µg/m³, 0.8× usual Otwock, 14 April: no reading Otwock, 15 April: no reading Kalisz Kalisz, 7 April: 10.2 µg/m³, 0.6× usual Kalisz, 8 April: 12.9 µg/m³, 0.8× usual Kalisz, 9 April: no reading Kalisz, 10 April: 29.2 µg/m³, 1.9× usual Kalisz, 11 April: 47.8 µg/m³, 3.0× usual Kalisz, 12 April: 34.7 µg/m³, 2.2× usual Kalisz, 13 April: 20.4 µg/m³, 1.3× usual Kalisz, 14 April: no reading Kalisz, 15 April: no reading Żywiec Żywiec, 7 April: 12.9 µg/m³, 0.8× usual Żywiec, 8 April: 16.4 µg/m³, 1.0× usual Żywiec, 9 April: no reading Żywiec, 10 April: 37.5 µg/m³, 2.3× usual Żywiec, 11 April: 37.5 µg/m³, 2.3× usual Żywiec, 12 April: 35.7 µg/m³, 2.2× usual Żywiec, 13 April: 20.8 µg/m³, 1.3× usual Żywiec, 14 April: no reading Żywiec, 15 April: no reading Łask Łask, 7 April: 10.6 µg/m³, 0.6× usual Łask, 8 April: 11.9 µg/m³, 0.7× usual Łask, 9 April: no reading Łask, 10 April: 18.5 µg/m³, 1.1× usual Łask, 11 April: 36.2 µg/m³, 2.2× usual Łask, 12 April: 29.3 µg/m³, 1.8× usual Łask, 13 April: 13.1 µg/m³, 0.8× usual Łask, 14 April: no reading Łask, 15 April: no reading Zgierz Zgierz, 7 April: 11.0 µg/m³, 0.8× usual Zgierz, 8 April: 12.8 µg/m³, 0.9× usual Zgierz, 9 April: 10.3 µg/m³, 0.7× usual Zgierz, 10 April: 18.5 µg/m³, 1.3× usual Zgierz, 11 April: 35.6 µg/m³, 2.5× usual Zgierz, 12 April: 24.6 µg/m³, 1.7× usual Zgierz, 13 April: 7.6 µg/m³, 0.5× usual Zgierz, 14 April: no reading Zgierz, 15 April: no reading Dębica Dębica, 7 April: 5.6 µg/m³, 0.4× usual Dębica, 8 April: 6.8 µg/m³, 0.5× usual Dębica, 9 April: 12.1 µg/m³, 0.9× usual Dębica, 10 April: 26.6 µg/m³, 1.9× usual Dębica, 11 April: 33.8 µg/m³, 2.5× usual Dębica, 12 April: 25.7 µg/m³, 1.9× usual Dębica, 13 April: 12.8 µg/m³, 0.9× usual Dębica, 14 April: no reading Dębica, 15 April: no reading Stodůlky Stodůlky, 7 April: 1.4 µg/m³, 0.1× usual Stodůlky, 8 April: 4.1 µg/m³, 0.3× usual Stodůlky, 9 April: 7.7 µg/m³, 0.6× usual Stodůlky, 10 April: 28.5 µg/m³, 2.1× usual Stodůlky, 11 April: 32.7 µg/m³, 2.4× usual Stodůlky, 12 April: 41.1 µg/m³, 3.0× usual Stodůlky, 13 April: 24.7 µg/m³, 1.8× usual Stodůlky, 14 April: 29.6 µg/m³, 2.1× usual Stodůlky, 15 April: 37.3 µg/m³, 2.7× usual Mielec Mielec, 7 April: 5.3 µg/m³, 0.4× usual Mielec, 8 April: 6.3 µg/m³, 0.5× usual Mielec, 9 April: 11.4 µg/m³, 0.9× usual Mielec, 10 April: 24.0 µg/m³, 1.9× usual Mielec, 11 April: 32.4 µg/m³, 2.6× usual Mielec, 12 April: 29.3 µg/m³, 2.4× usual Mielec, 13 April: 7.1 µg/m³, 0.6× usual Mielec, 14 April: no reading Mielec, 15 April: no reading Poznań Poznań, 7 April: 6.5 µg/m³, 0.5× usual Poznań, 8 April: 5.6 µg/m³, 0.4× usual Poznań, 9 April: no reading Poznań, 10 April: 17.4 µg/m³, 1.3× usual Poznań, 11 April: 31.5 µg/m³, 2.3× usual Poznań, 12 April: 28.5 µg/m³, 2.1× usual Poznań, 13 April: 15.1 µg/m³, 1.1× usual Poznań, 14 April: no reading Poznań, 15 April: no reading Rzeszów Rzeszów, 7 April: 7.3 µg/m³, 0.6× usual Rzeszów, 8 April: 6.6 µg/m³, 0.5× usual Rzeszów, 9 April: no reading Rzeszów, 10 April: 20.5 µg/m³, 1.7× usual Rzeszów, 11 April: 30.4 µg/m³, 2.5× usual Rzeszów, 12 April: 25.8 µg/m³, 2.1× usual Rzeszów, 13 April: 11.7 µg/m³, 0.9× usual Rzeszów, 14 April: no reading Rzeszów, 15 April: no reading Toruń Toruń, 7 April: 7.6 µg/m³, 0.5× usual Toruń, 8 April: 9.3 µg/m³, 0.6× usual Toruń, 9 April: 8.8 µg/m³, 0.6× usual Toruń, 10 April: 15.8 µg/m³, 1.1× usual Toruń, 11 April: 30.3 µg/m³, 2.1× usual Toruń, 12 April: 18.0 µg/m³, 1.3× usual Toruń, 13 April: 12.1 µg/m³, 0.8× usual Toruń, 14 April: no reading Toruń, 15 April: no reading Gorzów Wielkopolski Gorzów Wielkopolski, 7 April: 7.5 µg/m³, 0.7× usual Gorzów Wielkopolski, 8 April: 14.8 µg/m³, 1.5× usual Gorzów Wielkopolski, 9 April: 9.2 µg/m³, 0.9× usual Gorzów Wielkopolski, 10 April: 13.8 µg/m³, 1.4× usual Gorzów Wielkopolski, 11 April: 30.2 µg/m³, 3.0× usual Gorzów Wielkopolski, 12 April: 28.1 µg/m³, 2.8× usual Gorzów Wielkopolski, 13 April: 20.1 µg/m³, 2.0× usual Gorzów Wielkopolski, 14 April: no reading Gorzów Wielkopolski, 15 April: no reading Radom Radom, 7 April: 7.7 µg/m³, 0.5× usual Radom, 8 April: 8.7 µg/m³, 0.6× usual Radom, 9 April: 10.3 µg/m³, 0.7× usual Radom, 10 April: 17.0 µg/m³, 1.2× usual Radom, 11 April: 29.9 µg/m³, 2.1× usual Radom, 12 April: 22.1 µg/m³, 1.5× usual Radom, 13 April: 9.8 µg/m³, 0.7× usual Radom, 14 April: no reading Radom, 15 April: no reading Starachowice Starachowice, 7 April: 8.6 µg/m³, 0.6× usual Starachowice, 8 April: 9.6 µg/m³, 0.7× usual Starachowice, 9 April: no reading Starachowice, 10 April: 15.5 µg/m³, 1.1× usual Starachowice, 11 April: 29.4 µg/m³, 2.2× usual Starachowice, 12 April: 23.8 µg/m³, 1.8× usual Starachowice, 13 April: 10.8 µg/m³, 0.8× usual Starachowice, 14 April: no reading Starachowice, 15 April: no reading Krosno Krosno, 7 April: 5.9 µg/m³, 0.6× usual Krosno, 8 April: 11.9 µg/m³, 1.2× usual Krosno, 9 April: no reading Krosno, 10 April: 21.8 µg/m³, 2.1× usual Krosno, 11 April: 28.3 µg/m³, 2.7× usual Krosno, 12 April: 17.5 µg/m³, 1.7× usual Krosno, 13 April: 8.8 µg/m³, 0.9× usual Krosno, 14 April: no reading Krosno, 15 April: no reading Jarosław Jarosław, 7 April: 5.1 µg/m³, 0.4× usual Jarosław, 8 April: 6.1 µg/m³, 0.5× usual Jarosław, 9 April: no reading Jarosław, 10 April: 15.2 µg/m³, 1.2× usual Jarosław, 11 April: 27.9 µg/m³, 2.2× usual Jarosław, 12 April: 15.3 µg/m³, 1.2× usual Jarosław, 13 April: 6.7 µg/m³, 0.5× usual Jarosław, 14 April: no reading Jarosław, 15 April: no reading Kłodzko Kłodzko, 7 April: 11.3 µg/m³, 0.9× usual Kłodzko, 8 April: 11.0 µg/m³, 0.8× usual Kłodzko, 9 April: no reading Kłodzko, 10 April: 25.7 µg/m³, 2.0× usual Kłodzko, 11 April: 26.6 µg/m³, 2.0× usual Kłodzko, 12 April: 42.8 µg/m³, 3.3× usual Kłodzko, 13 April: 29.6 µg/m³, 2.3× usual Kłodzko, 14 April: no reading Kłodzko, 15 April: no reading Bydgoszcz Bydgoszcz, 7 April: 3.7 µg/m³, 0.3× usual Bydgoszcz, 8 April: 3.5 µg/m³, 0.3× usual Bydgoszcz, 9 April: 5.9 µg/m³, 0.5× usual Bydgoszcz, 10 April: 9.1 µg/m³, 0.8× usual Bydgoszcz, 11 April: 26.2 µg/m³, 2.2× usual Bydgoszcz, 12 April: 12.9 µg/m³, 1.1× usual Bydgoszcz, 13 April: 10.3 µg/m³, 0.9× usual Bydgoszcz, 14 April: no reading Bydgoszcz, 15 April: no reading Čadca Čadca, 7 April: no reading Čadca, 8 April: 9.6 µg/m³, 0.8× usual Čadca, 9 April: no reading Čadca, 10 April: 17.8 µg/m³, 1.6× usual Čadca, 11 April: 25.2 µg/m³, 2.2× usual Čadca, 12 April: 19.2 µg/m³, 1.7× usual Čadca, 13 April: 10.4 µg/m³, 0.9× usual Čadca, 14 April: 13.0 µg/m³, 1.2× usual Čadca, 15 April: no reading Racibórz Racibórz, 7 April: 5.4 µg/m³, 0.4× usual Racibórz, 8 April: 7.8 µg/m³, 0.6× usual Racibórz, 9 April: no reading Racibórz, 10 April: 26.0 µg/m³, 1.9× usual Racibórz, 11 April: 28.4 µg/m³, 2.0× usual Racibórz, 12 April: 31.7 µg/m³, 2.3× usual Racibórz, 13 April: 11.7 µg/m³, 0.8× usual Racibórz, 14 April: no reading Racibórz, 15 April: no reading Wrocław Wrocław, 7 April: 10.1 µg/m³, 0.8× usual Wrocław, 8 April: 10.3 µg/m³, 0.8× usual Wrocław, 9 April: 15.7 µg/m³, 1.2× usual Wrocław, 10 April: 25.0 µg/m³, 1.9× usual Wrocław, 11 April: 25.2 µg/m³, 1.9× usual Wrocław, 12 April: 31.6 µg/m³, 2.4× usual Wrocław, 13 April: 16.0 µg/m³, 1.2× usual Wrocław, 14 April: no reading Wrocław, 15 April: no reading Żary Żary, 7 April: 5.2 µg/m³, 0.6× usual Żary, 8 April: 9.3 µg/m³, 1.1× usual Żary, 9 April: 12.1 µg/m³, 1.4× usual Żary, 10 April: 19.8 µg/m³, 2.3× usual Żary, 11 April: 19.5 µg/m³, 2.2× usual Żary, 12 April: 30.2 µg/m³, 3.5× usual Żary, 13 April: 21.8 µg/m³, 2.5× usual Żary, 14 April: no reading Żary, 15 April: no reading Zielona Góra Zielona Góra, 7 April: 5.7 µg/m³, 0.5× usual Zielona Góra, 8 April: 6.4 µg/m³, 0.6× usual Zielona Góra, 9 April: 9.4 µg/m³, 0.9× usual Zielona Góra, 10 April: 13.9 µg/m³, 1.3× usual Zielona Góra, 11 April: 16.4 µg/m³, 1.5× usual Zielona Góra, 12 April: 26.3 µg/m³, 2.5× usual Zielona Góra, 13 April: 14.9 µg/m³, 1.4× usual Zielona Góra, 14 April: no reading Zielona Góra, 15 April: no reading Legionowo Legionowo, 7 April: 5.7 µg/m³, 0.4× usual Legionowo, 8 April: 6.0 µg/m³, 0.5× usual Legionowo, 9 April: 7.9 µg/m³, 0.6× usual Legionowo, 10 April: 16.4 µg/m³, 1.3× usual Legionowo, 11 April: 20.2 µg/m³, 1.6× usual Legionowo, 12 April: 25.8 µg/m³, 2.0× usual Legionowo, 13 April: 10.1 µg/m³, 0.8× usual Legionowo, 14 April: no reading Legionowo, 15 April: no reading 7 Apr 8 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
Radomsko Łódź Voivodeship, Poland 2 11 April 14.2 4.2× Brzeg Opole Voivodeship, Poland 3 12 April 9.6 3.9× Říčany Central Bohemia, Czechia 3 12 April 11.7 3.6× Otwock Mazovia, Poland 2 11 April 15.1 3.5× Żary Lubusz, Poland 1 12 April 8.7 3.5× Kłodzko Lower Silesia, Poland 2 12 April 13.0 3.3× Tarnów Lesser Poland, Poland 3 11 April 11.8 3.2× Kalisz Greater Poland, Poland 2 11 April 15.7 3.0× Gorzów Wielkopolski Lubusz, Poland 2 11 April 10.1 3.0× Stodůlky Prague, Czechia 2 12 April 13.9 3.0× Czechowice-Dziedzice Silesia, Poland 3 10 April 15.0 2.9× Krosno Subcarpathia, Poland 1 11 April 10.3 2.7× Kędzierzyn-Koźle Opole Voivodeship, Poland 3 11 April 11.7 2.6× Mielec Subcarpathia, Poland 2 11 April 12.4 2.6× Opole Opole Voivodeship, Poland 3 12 April 11.4 2.6× Zgierz Łódź Voivodeship, Poland 1 11 April 14.3 2.5× Zielona Góra Lubusz, Poland 1 12 April 10.6 2.5× Dębica Subcarpathia, Poland 1 11 April 13.7 2.5× Rzeszów Subcarpathia, Poland 2 11 April 12.4 2.5× Wrocław Lower Silesia, Poland 1 12 April 13.1 2.4× Jastrzębie Zdrój Silesia, Poland 2 10 April 18.3 2.3× Poznań Greater Poland, Poland 2 11 April 13.8 2.3× Racibórz Silesia, Poland 1 12 April 14.0 2.3× Żywiec Silesia, Poland 2 10 April 16.6 2.3× Čadca Žilina Region, Slovakia 1 11 April 11.3 2.2× Bydgoszcz Kujawsko-Pomorskie, Poland 1 11 April 11.8 2.2× Jarosław Subcarpathia, Poland 1 11 April 12.8 2.2× Łask Łódź Voivodeship, Poland 1 11 April 16.7 2.2× Starachowice Świętokrzyskie, Poland 1 11 April 13.6 2.2× Toruń Kujawsko-Pomorskie, Poland 1 11 April 14.4 2.1× Radom Mazovia, Poland 1 11 April 14.3 2.1× Legionowo Mazovia, Poland 1 12 April 12.7 2.0×
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 Poland and Czechia
Number 12 of 30 episodes in Poland and Czechia since our records began, by cities reached.
Eastern Europe, January 2025 123 Eastern Europe, December 2025 118 Eastern Europe, December 2023 107 Eastern Europe, November 2025 71 Eastern Europe, January 2026 70 Poland and Germany, January 2026 59 Eastern Europe, March 2023 56 North-eastern Europe, December 2025 55 Germany and Poland, February 2026 54 Eastern Europe, September 2023 51 Czechia and Slovakia, November and December 2023 41 Poland, April 2026 32 Bars: cities reached; colour: the level of the episode's highest daily reading. All 30 .
Use this page SmogRank, Poland, April 2026: 32 cities with PM2.5 at twice their usual or more, 10 to 12 April 2026, smogrank.com/episodes/2026-04-poland (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.
