SmogRank / Episodes / South Korea
South Korea and Japan, 11 to 14 May 2025
For 4 days, from 11 to 14 May 2025, 28 cities in South Korea and Japan had PM2.5 at least twice their usual for the time of year. The worst reading was Tamana, Kumamoto, Japan: 34.0 µg/m³ on 13 May, about 3.1× its usual 11.1.
No cause named We have no fire or smoke records for these days, so we only say what the measurements show.
Cities reached 28 in 2 countries
Days 4 11 to 14 May 2025
Worst day 12 May 11 cities counted
Furthest above usual 3.1× Tamana
Day by day
Play 12 May 11 cities at twice their usual or more
Naesŏ Changnyeong Changwon Kimhae Gyeongsan-si Sinhyeon Busan Chinju Hayang Ungsang Geoje Gijang Eisen Ulsan Gyeongju Kunwi Gimcheon Hadong Yeonil Gwangyang Pohang Kwangyang Changsu Sangju Yeosu Yeongdong Kurye Cheongsong gun Suncheon Andong Nangen Jinan-gun Mungyeong Yecheon Kinzan Imsil Beolgyo Tsushima Yeongju Jeonju Wanju Daejeon Damyang Koesan Boseong Namsa Hwasun Yŏnmu Cheongju-si Jeongeup Gwangju Chungju Iksan Kimje Masan Neietsu Jangseong Gongju Jangheung Chinch'ŏn Buan Koch'ang Buyeo Naju Gunsan Iki Cheonan Yeonggwang Seonghwan Asan Yeoju Santyoku Muan Yesan Pubal Pyeongtaek Boryeong Icheon-si Donghae City Mokpo Hongseong Osan Matsuura Yangp'yŏng Gangneung Karatsu Hongch’ŏn Gwangju Maebaru-chūō Itoshima Tangjin Imarichō-kō Sasebo Koga Seongnam-si Jumunjin Munakata Hwaseong-si Sinan Seosan Hanam Fukuoka Wabu Koga Hwado Taku Takeo Chuncheon Namyangju Wakasugi Nakama Saikai Kasuga Taesal-li Ureshinomachi-shimojuku Higashigō Nōgata Gotō Kashima Iizuka Kitakyushu Kanzakimachi-kanzaki Shimonoseki Saga Yanggu Jeju City Incheon Tosu Nagato Ogōri Sokcho Ōmura Tagawa Kurume Togitsu Hwacheon Yanagawa Obita Kanda Mine Chikugo Gimpo-si Yukuhashi Tanushimarumachi-toyoki Isahaya Nagasaki Seogwipo Onoda Ukiha Gaigeturi Yame Hagi Ōmuta Ube Arao Munsan Buzen Yamaguchi Cheorwon Hita Ganghwa-gun Nakatsu Yamaga Uekimachi-mōno Hōfu Kikuchi Kumamoto Masuda Ōyanomachi-noboritate Kotō Ōzu Uto Mifune Shūnan Aso Hamada Yufu Kudamatsu Beppu Kunisaki Hikari Gōtsuchō Ōita Tsurusaki Yanai Ōtake Iwakuni Mie Ōdachō-ōda Usuki Hiroshima Gion Yae Tsukumiura Saiki Kure Nobeoka Izumo Higashihiroshima Miyoshi Yawatahama Unnan Iyo Takehara Matsuyama Matsue Uwajima Mihara Imabari Sakaiminato Yasugichō Onomichi Yonago Shinagawa Shin’ichi Saijō Fukuyama Niimi Niihama Nakamura Kasaoka Susaki Shikokuchūō Ino Kochi Goseong Sejong Gwangmyeong Wŏnju Gumi Yangsan Yeongam Hwawŏn Anyang-si Nonsan Miryang Guri-si Seoul Waegwan Goyang-si Ansan-si Okcheon Yangju Gapyeong Haenam Jungpyong Daegu Uijeongbu-si Suwon Bucheon-si Tongyeong Anseong Tamana 8 May 9 10 11 12 13 14 15 16 17 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
Goyang-si Goyang-si, 8 May: 21.0 µg/m³ Goyang-si, 9 May: 15.8 µg/m³ Goyang-si, 10 May: 16.0 µg/m³ Goyang-si, 11 May: 32.8 µg/m³, 2.1× its usual 16.0 Goyang-si, 12 May: 32.6 µg/m³, 2.1× its usual 15.9 Goyang-si, 13 May: 26.2 µg/m³ Goyang-si, 14 May: 23.8 µg/m³ Goyang-si, 15 May: 19.8 µg/m³ Goyang-si, 16 May: 22.8 µg/m³ Goyang-si, 17 May: 10.3 µg/m³ Bucheon-si Bucheon-si, 8 May: 21.1 µg/m³ Bucheon-si, 9 May: 17.2 µg/m³ Bucheon-si, 10 May: 16.2 µg/m³ Bucheon-si, 11 May: 31.6 µg/m³, 2.1× its usual 15.2 Bucheon-si, 12 May: 33.1 µg/m³, 2.2× its usual 14.8 Bucheon-si, 13 May: 26.1 µg/m³ Bucheon-si, 14 May: 24.0 µg/m³ Bucheon-si, 15 May: 19.8 µg/m³ Bucheon-si, 16 May: 20.6 µg/m³ Bucheon-si, 17 May: 9.7 µg/m³ Guri-si Guri-si, 8 May: 22.8 µg/m³ Guri-si, 9 May: 17.5 µg/m³ Guri-si, 10 May: 13.9 µg/m³ Guri-si, 11 May: 31.6 µg/m³, 2.1× its usual 15.0 Guri-si, 12 May: 29.8 µg/m³ Guri-si, 13 May: 25.8 µg/m³ Guri-si, 14 May: 26.2 µg/m³ Guri-si, 15 May: 23.4 µg/m³ Guri-si, 16 May: 19.7 µg/m³ Guri-si, 17 May: 9.6 µg/m³ Seoul Seoul, 8 May: 20.9 µg/m³ Seoul, 9 May: 16.4 µg/m³ Seoul, 10 May: 14.3 µg/m³ Seoul, 11 May: 31.2 µg/m³, 2.0× its usual 15.5 Seoul, 12 May: 32.0 µg/m³, 2.1× its usual 15.4 Seoul, 13 May: 26.1 µg/m³ Seoul, 14 May: 25.8 µg/m³ Seoul, 15 May: 22.0 µg/m³ Seoul, 16 May: 23.3 µg/m³ Seoul, 17 May: 9.3 µg/m³ Uijeongbu-si Uijeongbu-si, 8 May: 21.2 µg/m³ Uijeongbu-si, 9 May: 18.2 µg/m³ Uijeongbu-si, 10 May: 11.2 µg/m³ Uijeongbu-si, 11 May: 30.8 µg/m³, 2.2× its usual 13.9 Uijeongbu-si, 12 May: 27.3 µg/m³ Uijeongbu-si, 13 May: 21.6 µg/m³ Uijeongbu-si, 14 May: 23.8 µg/m³ Uijeongbu-si, 15 May: 18.1 µg/m³ Uijeongbu-si, 16 May: 19.6 µg/m³ Uijeongbu-si, 17 May: 7.5 µg/m³ Wŏnju Wŏnju, 8 May: 25.4 µg/m³ Wŏnju, 9 May: 21.6 µg/m³ Wŏnju, 10 May: 12.6 µg/m³ Wŏnju, 11 May: 29.9 µg/m³, 2.0× its usual 15.0 Wŏnju, 12 May: 28.1 µg/m³ Wŏnju, 13 May: 26.6 µg/m³ Wŏnju, 14 May: 25.9 µg/m³ Wŏnju, 15 May: 22.4 µg/m³ Wŏnju, 16 May: 17.4 µg/m³ Wŏnju, 17 May: 10.0 µg/m³ Anyang-si Anyang-si, 8 May: 20.2 µg/m³ Anyang-si, 9 May: 15.9 µg/m³ Anyang-si, 10 May: 15.2 µg/m³ Anyang-si, 11 May: 29.1 µg/m³, 2.0× its usual 14.6 Anyang-si, 12 May: 29.9 µg/m³, 2.1× its usual 14.5 Anyang-si, 13 May: 24.7 µg/m³ Anyang-si, 14 May: 23.3 µg/m³ Anyang-si, 15 May: 21.3 µg/m³ Anyang-si, 16 May: 13.8 µg/m³ Anyang-si, 17 May: 8.5 µg/m³ Gapyeong Gapyeong, 8 May: 17.4 µg/m³ Gapyeong, 9 May: 16.9 µg/m³ Gapyeong, 10 May: 6.8 µg/m³ Gapyeong, 11 May: 26.5 µg/m³, 2.2× its usual 11.8 Gapyeong, 12 May: 22.5 µg/m³ Gapyeong, 13 May: 20.0 µg/m³ Gapyeong, 14 May: 19.8 µg/m³ Gapyeong, 15 May: 18.1 µg/m³ Gapyeong, 16 May: 15.8 µg/m³ Gapyeong, 17 May: 7.7 µg/m³ Yangju Yangju, 8 May: 19.1 µg/m³ Yangju, 9 May: 15.8 µg/m³ Yangju, 10 May: 6.9 µg/m³ Yangju, 11 May: 26.4 µg/m³, 2.2× its usual 11.8 Yangju, 12 May: 23.7 µg/m³ Yangju, 13 May: 22.0 µg/m³ Yangju, 14 May: 21.5 µg/m³ Yangju, 15 May: 15.4 µg/m³ Yangju, 16 May: 13.7 µg/m³ Yangju, 17 May: 5.0 µg/m³ Okcheon Okcheon, 8 May: 23.8 µg/m³ Okcheon, 9 May: 12.6 µg/m³ Okcheon, 10 May: 7.5 µg/m³ Okcheon, 11 May: 25.1 µg/m³, 2.1× its usual 12.0 Okcheon, 12 May: 23.7 µg/m³ Okcheon, 13 May: 26.0 µg/m³, 2.2× its usual 12.0 Okcheon, 14 May: 26.0 µg/m³, 2.2× its usual 11.9 Okcheon, 15 May: 13.0 µg/m³ Okcheon, 16 May: 6.7 µg/m³ Okcheon, 17 May: 10.3 µg/m³ Ansan-si Ansan-si, 8 May: 22.2 µg/m³ Ansan-si, 9 May: 17.0 µg/m³ Ansan-si, 10 May: 17.2 µg/m³ Ansan-si, 11 May: 30.8 µg/m³ Ansan-si, 12 May: 32.9 µg/m³, 2.1× its usual 15.9 Ansan-si, 13 May: 25.6 µg/m³ Ansan-si, 14 May: 24.5 µg/m³ Ansan-si, 15 May: 21.1 µg/m³ Ansan-si, 16 May: 17.9 µg/m³ Ansan-si, 17 May: 11.4 µg/m³ Suwon Suwon, 8 May: 22.9 µg/m³ Suwon, 9 May: 15.7 µg/m³ Suwon, 10 May: 14.5 µg/m³ Suwon, 11 May: 26.4 µg/m³ Suwon, 12 May: 32.3 µg/m³, 2.2× its usual 14.8 Suwon, 13 May: 27.1 µg/m³ Suwon, 14 May: 26.7 µg/m³ Suwon, 15 May: 22.4 µg/m³ Suwon, 16 May: 10.1 µg/m³ Suwon, 17 May: 7.4 µg/m³ Anseong Anseong, 8 May: 24.4 µg/m³ Anseong, 9 May: 14.9 µg/m³ Anseong, 10 May: 13.2 µg/m³ Anseong, 11 May: 21.5 µg/m³ Anseong, 12 May: 30.4 µg/m³, 2.3× its usual 13.1 Anseong, 13 May: 26.2 µg/m³ Anseong, 14 May: 26.2 µg/m³ Anseong, 15 May: 10.4 µg/m³ Anseong, 16 May: 6.1 µg/m³ Anseong, 17 May: 2.9 µg/m³ Gwangmyeong Gwangmyeong, 8 May: 18.5 µg/m³ Gwangmyeong, 9 May: 15.7 µg/m³ Gwangmyeong, 10 May: 13.1 µg/m³ Gwangmyeong, 11 May: 29.5 µg/m³ Gwangmyeong, 12 May: 29.8 µg/m³, 2.0× its usual 14.8 Gwangmyeong, 13 May: 24.8 µg/m³ Gwangmyeong, 14 May: 23.6 µg/m³ Gwangmyeong, 15 May: 20.8 µg/m³ Gwangmyeong, 16 May: 21.0 µg/m³ Gwangmyeong, 17 May: 6.6 µg/m³ Jungpyong Jungpyong, 8 May: 25.9 µg/m³ Jungpyong, 9 May: 16.1 µg/m³ Jungpyong, 10 May: 10.5 µg/m³ Jungpyong, 11 May: 26.3 µg/m³ Jungpyong, 12 May: 29.5 µg/m³, 2.2× its usual 13.4 Jungpyong, 13 May: 26.3 µg/m³ Jungpyong, 14 May: 27.1 µg/m³, 2.0× its usual 13.5 Jungpyong, 15 May: 21.7 µg/m³ Jungpyong, 16 May: 8.3 µg/m³ Jungpyong, 17 May: 10.2 µg/m³ Haenam Haenam, 8 May: 10.0 µg/m³ Haenam, 9 May: 8.5 µg/m³ Haenam, 10 May: 12.0 µg/m³ Haenam, 11 May: 20.8 µg/m³ Haenam, 12 May: 29.0 µg/m³, 2.2× its usual 13.0 Haenam, 13 May: 26.0 µg/m³ Haenam, 14 May: 20.3 µg/m³ Haenam, 15 May: 9.6 µg/m³ Haenam, 16 May: 8.0 µg/m³ Haenam, 17 May: no reading Tongyeong Tongyeong, 8 May: 16.9 µg/m³ Tongyeong, 9 May: 8.5 µg/m³ Tongyeong, 10 May: 8.8 µg/m³ Tongyeong, 11 May: 24.5 µg/m³ Tongyeong, 12 May: 27.3 µg/m³, 2.2× its usual 12.5 Tongyeong, 13 May: 29.0 µg/m³, 2.3× its usual 12.4 Tongyeong, 14 May: 24.1 µg/m³ Tongyeong, 15 May: 21.0 µg/m³ Tongyeong, 16 May: 14.3 µg/m³ Tongyeong, 17 May: 9.2 µg/m³ Tamana Tamana, 8 May: 15.2 µg/m³ Tamana, 9 May: 9.1 µg/m³ Tamana, 10 May: 12.0 µg/m³ Tamana, 11 May: 1.8 µg/m³ Tamana, 12 May: 19.7 µg/m³ Tamana, 13 May: 34.0 µg/m³, 3.1× its usual 11.1 Tamana, 14 May: 32.4 µg/m³ Tamana, 15 May: 17.5 µg/m³ Tamana, 16 May: 23.0 µg/m³ Tamana, 17 May: 8.3 µg/m³ Waegwan Waegwan, 8 May: 22.2 µg/m³ Waegwan, 9 May: 15.3 µg/m³ Waegwan, 10 May: 9.6 µg/m³ Waegwan, 11 May: 16.2 µg/m³ Waegwan, 12 May: 21.5 µg/m³ Waegwan, 13 May: 32.6 µg/m³, 2.1× its usual 15.2 Waegwan, 14 May: 31.0 µg/m³, 2.0× its usual 15.2 Waegwan, 15 May: 23.6 µg/m³ Waegwan, 16 May: 16.3 µg/m³ Waegwan, 17 May: 15.1 µg/m³ Miryang Miryang, 8 May: 15.6 µg/m³ Miryang, 9 May: 12.5 µg/m³ Miryang, 10 May: 8.2 µg/m³ Miryang, 11 May: 14.6 µg/m³ Miryang, 12 May: 19.8 µg/m³ Miryang, 13 May: 30.6 µg/m³, 2.1× its usual 14.8 Miryang, 14 May: 28.2 µg/m³ Miryang, 15 May: 24.1 µg/m³ Miryang, 16 May: 20.2 µg/m³ Miryang, 17 May: 17.8 µg/m³ Nonsan Nonsan, 8 May: 19.0 µg/m³ Nonsan, 9 May: 12.0 µg/m³ Nonsan, 10 May: 11.0 µg/m³ Nonsan, 11 May: 22.3 µg/m³ Nonsan, 12 May: 25.6 µg/m³ Nonsan, 13 May: 30.3 µg/m³, 2.1× its usual 14.5 Nonsan, 14 May: 26.5 µg/m³ Nonsan, 15 May: 13.1 µg/m³ Nonsan, 16 May: 8.1 µg/m³ Nonsan, 17 May: 8.0 µg/m³ Daegu Daegu, 8 May: 20.3 µg/m³ Daegu, 9 May: 12.0 µg/m³ Daegu, 10 May: 5.8 µg/m³ Daegu, 11 May: 14.7 µg/m³ Daegu, 12 May: 20.7 µg/m³ Daegu, 13 May: 30.0 µg/m³, 2.2× its usual 13.5 Daegu, 14 May: 27.7 µg/m³, 2.1× its usual 13.0 Daegu, 15 May: 17.3 µg/m³ Daegu, 16 May: 13.8 µg/m³ Daegu, 17 May: 14.4 µg/m³ Hwawŏn Hwawŏn, 8 May: 19.9 µg/m³ Hwawŏn, 9 May: 13.3 µg/m³ Hwawŏn, 10 May: 4.9 µg/m³ Hwawŏn, 11 May: 14.0 µg/m³ Hwawŏn, 12 May: 19.2 µg/m³ Hwawŏn, 13 May: 28.7 µg/m³, 2.1× its usual 13.4 Hwawŏn, 14 May: 18.7 µg/m³ Hwawŏn, 15 May: 19.0 µg/m³ Hwawŏn, 16 May: 14.9 µg/m³ Hwawŏn, 17 May: 15.1 µg/m³ Yeongam Yeongam, 8 May: 9.1 µg/m³ Yeongam, 9 May: 7.6 µg/m³ Yeongam, 10 May: 12.7 µg/m³ Yeongam, 11 May: 21.5 µg/m³ Yeongam, 12 May: 23.6 µg/m³ Yeongam, 13 May: 26.5 µg/m³, 2.1× its usual 12.5 Yeongam, 14 May: 19.6 µg/m³ Yeongam, 15 May: 10.2 µg/m³ Yeongam, 16 May: 7.3 µg/m³ Yeongam, 17 May: 9.1 µg/m³ Yangsan Yangsan, 8 May: 13.5 µg/m³ Yangsan, 9 May: 8.0 µg/m³ Yangsan, 10 May: 6.3 µg/m³ Yangsan, 11 May: 14.3 µg/m³ Yangsan, 12 May: 18.8 µg/m³ Yangsan, 13 May: 26.2 µg/m³, 2.1× its usual 12.6 Yangsan, 14 May: 25.1 µg/m³ Yangsan, 15 May: 19.4 µg/m³ Yangsan, 16 May: 14.7 µg/m³ Yangsan, 17 May: 15.6 µg/m³ Goseong Goseong, 8 May: 15.2 µg/m³ Goseong, 9 May: 10.1 µg/m³ Goseong, 10 May: 10.4 µg/m³ Goseong, 11 May: 22.9 µg/m³ Goseong, 12 May: 23.1 µg/m³ Goseong, 13 May: 26.1 µg/m³, 2.0× its usual 12.9 Goseong, 14 May: 22.6 µg/m³ Goseong, 15 May: 19.5 µg/m³ Goseong, 16 May: 14.5 µg/m³ Goseong, 17 May: 9.5 µg/m³ Gumi Gumi, 8 May: 25.0 µg/m³ Gumi, 9 May: 17.3 µg/m³ Gumi, 10 May: 10.7 µg/m³ Gumi, 11 May: 19.3 µg/m³ Gumi, 12 May: 26.7 µg/m³ Gumi, 13 May: 28.9 µg/m³ Gumi, 14 May: 30.9 µg/m³, 2.0× its usual 15.3 Gumi, 15 May: 26.4 µg/m³ Gumi, 16 May: 17.7 µg/m³ Gumi, 17 May: 13.7 µg/m³ Sejong Sejong, 8 May: 25.5 µg/m³ Sejong, 9 May: 12.1 µg/m³ Sejong, 10 May: 8.8 µg/m³ Sejong, 11 May: 23.2 µg/m³ Sejong, 12 May: 24.9 µg/m³ Sejong, 13 May: 27.1 µg/m³ Sejong, 14 May: 28.0 µg/m³, 2.0× its usual 13.9 Sejong, 15 May: 14.3 µg/m³ Sejong, 16 May: 7.3 µg/m³ Sejong, 17 May: 8.5 µg/m³ 8 May 9 10 11 12 13 14 15 16 17 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
Tamana Kumamoto, Japan 1 13 May 11.1 3.1× Anseong Gyeonggi-do, South Korea 1 12 May 13.1 2.3× Tongyeong Gyeongsangnam-do, South Korea 2 13 May 12.4 2.3× Bucheon-si Gyeonggi-do, South Korea 2 12 May 14.8 2.2× Suwon Gyeonggi-do, South Korea 1 12 May 14.8 2.2× Uijeongbu-si Gyeonggi-do, South Korea 1 11 May 13.9 2.2× Daegu Daegu, South Korea 2 13 May 13.5 2.2× Jungpyong North Chungcheong, South Korea 2 12 May 13.4 2.2× Haenam Jeollanam-do, South Korea 1 12 May 13.0 2.2× Gapyeong Gyeonggi-do, South Korea 1 11 May 11.8 2.2× Yangju Gyeonggi-do, South Korea 1 11 May 11.8 2.2× Okcheon North Chungcheong, South Korea 3 13 May 12.0 2.2× Ansan-si Gyeonggi-do, South Korea 1 12 May 15.9 2.1× Goyang-si Gyeonggi-do, South Korea 2 11 May 16.0 2.1× Waegwan Gyeongsangbuk-do, South Korea 2 13 May 15.2 2.1× Seoul Seoul, South Korea 2 12 May 15.4 2.1× Guri-si Gyeonggi-do, South Korea 1 11 May 15.0 2.1× Miryang Gyeongsangnam-do, South Korea 1 13 May 14.8 2.1× Nonsan Chungcheongnam-do, South Korea 1 13 May 14.5 2.1× Anyang-si Gyeonggi-do, South Korea 2 12 May 14.5 2.1× Hwawŏn Daegu, South Korea 1 13 May 13.4 2.1× Yeongam Jeollanam-do, South Korea 1 13 May 12.5 2.1× Yangsan Gyeongsangnam-do, South Korea 1 13 May 12.6 2.1× Gumi Gyeongsangbuk-do, South Korea 1 14 May 15.3 2.0× Wŏnju Gangwon-do, South Korea 1 11 May 15.0 2.0× Gwangmyeong Gyeonggi-do, South Korea 1 12 May 14.8 2.0× Sejong Sejong-si, South Korea 1 14 May 13.9 2.0× Goseong Gyeongsangnam-do, South Korea 1 13 May 12.9 2.0×
Daily means in µg/m³, over the days each city counted in this episode. Highest: its highest of those days. Usual: the city's median for the time of year of that day (its days within 21 days of the date, every year, leaving out the week around it). Above usual: its highest day against that, with a usual under 5 µg/m³ taken as 5.
Against other episodes in South Korea and Japan
Number 51 of 94 episodes in South Korea and Japan since our records began, by cities reached.
Japan and South Korea, June and July 2025 508 Japan and South Korea, April 2024 499 Japan and South Korea, March 2025 454 Japan and South Korea, March 2026 305 Japan and South Korea, January 2025 274 Japan and South Korea, February and March 2025 192 Japan, 21 to 25 July 2026 172 South Korea and Japan, January 2026 169 South Korea and Japan, 10 to 15 February 2026 147 South Korea, 14 to 16 February 2025 132 Japan, November 2023 131 South Korea and Japan, November 2025 128 South Korea and Japan, 11 to 14 May 2025 28 Bars: cities reached; colour: the level of the episode's highest daily reading. All 94 .
Use this page SmogRank, South Korea and Japan, 11 to 14 May 2025: 28 cities with PM2.5 at twice their usual or more, 11 to 14 May 2025, smogrank.com/episodes/2025-05-11-south-korea-and-japan (accessed 4 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.
