SmogRank / Episodes / Japan
Japan, December 2025
For 2 days, from 20 to 21 December 2025, 47 cities in Japan had PM2.5 at least twice their usual for the time of year. The worst reading was Tsuchiura, Ibaraki, Japan: 47.6 µg/m³ on 21 December, about 5.0× its usual 9.6.
No cause named We have no fire or smoke records for these days, so we only say what the measurements show.
Cities reached 47 in 1 country
Days 2 20 to 21 December 2025
Worst day 21 December 34 cities counted
Furthest above usual 5.3× Toride
Day by day
Play 21 December 34 cities at twice their usual or more
Kawagoe Tokorozawa Higashikurume Sayama Higashimurayama Kodaira Sakado Higashi-Matsuyama Iruma Yokota Fuchū Tokyo Hannō Akishima Morohongō Noborito Kumagaya Azamino Koga Hachiōji Ōme Ogawamachi Machida Menuma Aihara Urayasu Minamirinkan Yorii Yamato Minawa Ashikaga Yokohama Ayase Sakai-nakajima Atsugi Chichibu Honjō Tochigi Narashino Kodamachō-kodamaminami Ebina Fujisawa Isehara Kiryū Chigasaki Kamakura Hiratsuka Yokosuka Hadano Kaminokawa Ōtsuki Ajiki Kurihama Kanuma Minamiashigara Utsunomiya Miura Tomioka Narita Inashiki Shibukawa Imaichi Gotemba Kasama Mobara Tōgane Fujiyoshida Yamanashi Numata Minamibōsō Sawara Yokoshiba Atami Tateyama Nasukarasuyama Susono Yaita Mito Sōsa Nakanojō Ōhara Izunokuni Omigawa Numazu Katsuura Hitachiomiya Kashima-shi Saku Fuji Fujinomiya Nasushiobara Hitachi Shimoda Minamiuonuma Ueda Shirakawa Suwa Suzaka Kitaibaraki Shizuoka Okaya Nagano Chikuma Ina Matsumoto Aizu-Wakamatsu Fujieda Nagaoka Kōriyama Shimada Iwaki Iida Jōetsu Kikugawa Kakegawa Shirone Niitsu-honchō Maki Fukuroi Kameda-honchō Itoigawa Fukushima Shibata Iwata Hamakita Yonezawa Niigata Hamamatsu Minami-Sōma Nagai Shinshiro Nyūzen Takayama Gero Sōma Uozu Shiroishi Kosai Namerikawa Kakuda Toki Sado Toyohashi Yamagata Toyama Tajimi Toyota Seto Kani Gamagōri Iwanuma Minokamo Okazaki Imizu Tahara Nisshin Owariasahi Natori-shi Anjō Inuyama Sekimachi Chiryū Takaoka Sendai Nishio Tonami Kariya Kakamigahara Himimachi Nagoya Hekinan Tōkai Tagajō-shi Handa Oyabe Ichinomiya Minamichita Nanao Gifu Ama Tokoname Kaminoma Tsubata Mizuho Hashima Hakui Anamizu Ōgaki Kaizu Kuwana Nonoichi Ibi Kanazawa Matsutō Toba Ono Yokkaichi Inabe Shima Suzuka Komatsu Ise Saikū Kaga Tsu Kameyama Matsusaka Nagahama Fukui-shi Hikone Sabae Mikuni Youkaichi Tsuruga Kōka Ōmihachiman Takashima Iga Ueno-ebisumachi Kusatsu Nabari Kitahama Ōtsu Owase Obama Uji Kizugawa Jōyō Kyoto Sugai Nara-shi Tenri Kumano Kōtari Yawata Kashihara-shi Hōryūji Ikoma Hirakata Kashiwara Kameoka Takatsuki Nantan Yao Higashiosaka Shingū Yono Habikino Tondabayashichō Sayama Osaka Kawachi-Nagano Toyonaka Hashimoto Maizuru Sakai Amagasaki Takarazuka Ayabe Izumi Miyazu Nishinomiya Kishiwada Sandachō Kinokawa Fukuchiyama Izumisano Kyōtango Kobe Iwade Sennan Nishiwaki Kainan Tanabe Minato Akashi Ono Toyooka Arida Higashinozoe Gobō Kakogawachō-honmachi Sumoto Himeji Ikaruga Tatsuno Narutochō-mitsuishi Anan Tokushima Gyōda Igusa Niiza Kofu Kamagaya Chikusei Asaka Ōta Yachiyo Inzai Chiba Yachimata Kōnosu Yotsukaidō Kawaguchi Bandō Ageo Kazo Matsudo Saitama Misato, Saitama Kamisu Oyama Minami-Alps Sakura Kasukabe Kukichūō Mooka Kisarazu Tatebayashi Hokota Ichihara Shimo-tsuma Sodegaura Jōsō Koshigaya Noda Hanyū Kashiwa Sōka Ishioka Kimitsu Sano Naka Tsuchiura Hitachi-Naka Toride 17 Dec 18 19 20 21 22 23 24 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
Jōsō Jōsō, 17 December: 17.8 µg/m³, 1.8× usual Jōsō, 18 December: 8.9 µg/m³, 0.9× usual Jōsō, 19 December: 16.5 µg/m³, 1.7× usual Jōsō, 20 December: 39.0 µg/m³, 3.9× usual Jōsō, 21 December: 40.9 µg/m³, 4.1× usual Jōsō, 22 December: 6.1 µg/m³, 0.6× usual Jōsō, 23 December: 9.1 µg/m³, 0.9× usual Jōsō, 24 December: 12.9 µg/m³, 1.3× usual Tsuchiura Tsuchiura, 17 December: 16.5 µg/m³, 1.7× usual Tsuchiura, 18 December: no reading Tsuchiura, 19 December: 9.5 µg/m³, 1.0× usual Tsuchiura, 20 December: 37.6 µg/m³, 3.9× usual Tsuchiura, 21 December: 47.6 µg/m³, 5.0× usual Tsuchiura, 22 December: 6.2 µg/m³, 0.6× usual Tsuchiura, 23 December: 8.6 µg/m³, 0.9× usual Tsuchiura, 24 December: 15.5 µg/m³, 1.6× usual Naka Naka, 17 December: 14.2 µg/m³, 1.5× usual Naka, 18 December: 11.6 µg/m³, 1.2× usual Naka, 19 December: 10.9 µg/m³, 1.2× usual Naka, 20 December: 36.1 µg/m³, 3.9× usual Naka, 21 December: 42.9 µg/m³, 4.6× usual Naka, 22 December: 3.9 µg/m³, 0.4× usual Naka, 23 December: 9.5 µg/m³, 1.0× usual Naka, 24 December: 14.0 µg/m³, 1.5× usual Shimo-tsuma Shimo-tsuma, 17 December: 14.7 µg/m³, 1.5× usual Shimo-tsuma, 18 December: 7.7 µg/m³, 0.8× usual Shimo-tsuma, 19 December: 12.7 µg/m³, 1.3× usual Shimo-tsuma, 20 December: 36.1 µg/m³, 3.6× usual Shimo-tsuma, 21 December: 39.9 µg/m³, 4.0× usual Shimo-tsuma, 22 December: no reading Shimo-tsuma, 23 December: 10.2 µg/m³, 1.0× usual Shimo-tsuma, 24 December: 14.6 µg/m³, 1.4× usual Chikusei Chikusei, 17 December: 17.0 µg/m³, 1.5× usual Chikusei, 18 December: 7.1 µg/m³, 0.6× usual Chikusei, 19 December: 17.4 µg/m³, 1.5× usual Chikusei, 20 December: 35.3 µg/m³, 3.1× usual Chikusei, 21 December: 34.5 µg/m³, 3.1× usual Chikusei, 22 December: 2.5 µg/m³, 0.2× usual Chikusei, 23 December: 11.8 µg/m³, 1.0× usual Chikusei, 24 December: 13.9 µg/m³, 1.2× usual Toride Toride, 17 December: 14.6 µg/m³, 1.8× usual Toride, 18 December: 9.2 µg/m³, 1.2× usual Toride, 19 December: 13.7 µg/m³, 1.7× usual Toride, 20 December: 31.9 µg/m³, 4.0× usual Toride, 21 December: 42.4 µg/m³, 5.3× usual Toride, 22 December: 4.1 µg/m³, 0.5× usual Toride, 23 December: 8.9 µg/m³, 1.1× usual Toride, 24 December: 13.4 µg/m³, 1.7× usual Hitachi-Naka Hitachi-Naka, 17 December: 10.3 µg/m³, 1.8× usual Hitachi-Naka, 18 December: 3.5 µg/m³, 0.6× usual Hitachi-Naka, 19 December: 5.9 µg/m³, 1.0× usual Hitachi-Naka, 20 December: 30.0 µg/m³, 5.2× usual Hitachi-Naka, 21 December: 12.9 µg/m³, 2.2× usual Hitachi-Naka, 22 December: 2.4 µg/m³, 0.4× usual Hitachi-Naka, 23 December: 5.2 µg/m³, 0.9× usual Hitachi-Naka, 24 December: 6.0 µg/m³, 1.0× usual Hokota Hokota, 17 December: 8.9 µg/m³, 1.2× usual Hokota, 18 December: 4.4 µg/m³, 0.6× usual Hokota, 19 December: 6.9 µg/m³, 0.9× usual Hokota, 20 December: 29.7 µg/m³, 4.0× usual Hokota, 21 December: 25.8 µg/m³, 3.5× usual Hokota, 22 December: 3.8 µg/m³, 0.5× usual Hokota, 23 December: 8.2 µg/m³, 1.1× usual Hokota, 24 December: 12.2 µg/m³, 1.6× usual Yotsukaidō Yotsukaidō, 17 December: 19.5 µg/m³, 2.1× usual Yotsukaidō, 18 December: 15.7 µg/m³, 1.7× usual Yotsukaidō, 19 December: 12.1 µg/m³, 1.3× usual Yotsukaidō, 20 December: 29.7 µg/m³, 3.3× usual Yotsukaidō, 21 December: 20.1 µg/m³, 2.2× usual Yotsukaidō, 22 December: 3.2 µg/m³, 0.4× usual Yotsukaidō, 23 December: 7.0 µg/m³, 0.8× usual Yotsukaidō, 24 December: 14.1 µg/m³, 1.5× usual Yachiyo Yachiyo, 17 December: 16.0 µg/m³, 1.7× usual Yachiyo, 18 December: 12.5 µg/m³, 1.3× usual Yachiyo, 19 December: 13.4 µg/m³, 1.4× usual Yachiyo, 20 December: 29.4 µg/m³, 3.2× usual Yachiyo, 21 December: 19.5 µg/m³, 2.1× usual Yachiyo, 22 December: 3.1 µg/m³, 0.3× usual Yachiyo, 23 December: 7.9 µg/m³, 0.8× usual Yachiyo, 24 December: 10.8 µg/m³, 1.2× usual Kimitsu Kimitsu, 17 December: 9.6 µg/m³, 1.5× usual Kimitsu, 18 December: 7.2 µg/m³, 1.1× usual Kimitsu, 19 December: 12.2 µg/m³, 1.8× usual Kimitsu, 20 December: 29.3 µg/m³, 4.4× usual Kimitsu, 21 December: 10.6 µg/m³, 1.6× usual Kimitsu, 22 December: 5.0 µg/m³, 0.8× usual Kimitsu, 23 December: 7.7 µg/m³, 1.2× usual Kimitsu, 24 December: 11.7 µg/m³, 1.8× usual Oyama Oyama, 17 December: 14.6 µg/m³, 1.5× usual Oyama, 18 December: 9.4 µg/m³, 1.0× usual Oyama, 19 December: 11.8 µg/m³, 1.2× usual Oyama, 20 December: 28.5 µg/m³, 3.0× usual Oyama, 21 December: 35.7 µg/m³, 3.7× usual Oyama, 22 December: 4.5 µg/m³, 0.5× usual Oyama, 23 December: 9.5 µg/m³, 1.0× usual Oyama, 24 December: 14.2 µg/m³, 1.5× usual Sakura Sakura, 17 December: 16.2 µg/m³, 2.2× usual Sakura, 18 December: 11.1 µg/m³, 1.5× usual Sakura, 19 December: 10.3 µg/m³, 1.4× usual Sakura, 20 December: 28.2 µg/m³, 3.8× usual Sakura, 21 December: 16.1 µg/m³, 2.2× usual Sakura, 22 December: 3.1 µg/m³, 0.4× usual Sakura, 23 December: 7.0 µg/m³, 0.9× usual Sakura, 24 December: 9.7 µg/m³, 1.3× usual Kisarazu Kisarazu, 17 December: 11.1 µg/m³, 1.5× usual Kisarazu, 18 December: 7.7 µg/m³, 1.1× usual Kisarazu, 19 December: 12.7 µg/m³, 1.8× usual Kisarazu, 20 December: 27.9 µg/m³, 3.9× usual Kisarazu, 21 December: 10.9 µg/m³, 1.5× usual Kisarazu, 22 December: 4.4 µg/m³, 0.6× usual Kisarazu, 23 December: 6.7 µg/m³, 0.9× usual Kisarazu, 24 December: 9.3 µg/m³, 1.3× usual Kamisu Kamisu, 17 December: 13.0 µg/m³, 1.7× usual Kamisu, 18 December: 5.1 µg/m³, 0.7× usual Kamisu, 19 December: 6.4 µg/m³, 0.9× usual Kamisu, 20 December: 27.8 µg/m³, 3.7× usual Kamisu, 21 December: 7.9 µg/m³, 1.1× usual Kamisu, 22 December: 4.0 µg/m³, 0.5× usual Kamisu, 23 December: 5.4 µg/m³, 0.7× usual Kamisu, 24 December: 17.1 µg/m³, 2.3× usual Ishioka Ishioka, 17 December: 9.9 µg/m³, 1.3× usual Ishioka, 18 December: 7.1 µg/m³, 0.9× usual Ishioka, 19 December: 10.0 µg/m³, 1.3× usual Ishioka, 20 December: 27.2 µg/m³, 3.5× usual Ishioka, 21 December: 34.5 µg/m³, 4.4× usual Ishioka, 22 December: 3.2 µg/m³, 0.4× usual Ishioka, 23 December: 6.3 µg/m³, 0.8× usual Ishioka, 24 December: 9.3 µg/m³, 1.2× usual Ichihara Ichihara, 17 December: 13.1 µg/m³, 1.9× usual Ichihara, 18 December: 8.0 µg/m³, 1.2× usual Ichihara, 19 December: 8.8 µg/m³, 1.3× usual Ichihara, 20 December: 27.1 µg/m³, 4.0× usual Ichihara, 21 December: 13.0 µg/m³, 1.9× usual Ichihara, 22 December: 3.5 µg/m³, 0.5× usual Ichihara, 23 December: 6.6 µg/m³, 1.0× usual Ichihara, 24 December: 11.7 µg/m³, 1.7× usual Kamagaya Kamagaya, 17 December: 16.7 µg/m³, 1.9× usual Kamagaya, 18 December: 10.5 µg/m³, 1.2× usual Kamagaya, 19 December: 14.6 µg/m³, 1.6× usual Kamagaya, 20 December: 27.0 µg/m³, 3.0× usual Kamagaya, 21 December: 27.6 µg/m³, 3.1× usual Kamagaya, 22 December: 4.3 µg/m³, 0.5× usual Kamagaya, 23 December: 8.5 µg/m³, 1.0× usual Kamagaya, 24 December: 10.6 µg/m³, 1.2× usual Yachimata Yachimata, 17 December: 14.6 µg/m³, 1.8× usual Yachimata, 18 December: 11.5 µg/m³, 1.4× usual Yachimata, 19 December: 10.2 µg/m³, 1.2× usual Yachimata, 20 December: 26.7 µg/m³, 3.2× usual Yachimata, 21 December: 10.4 µg/m³, 1.3× usual Yachimata, 22 December: 3.6 µg/m³, 0.4× usual Yachimata, 23 December: 7.8 µg/m³, 0.9× usual Yachimata, 24 December: 12.6 µg/m³, 1.5× usual Sodegaura Sodegaura, 17 December: 11.4 µg/m³, 1.8× usual Sodegaura, 18 December: 5.7 µg/m³, 0.9× usual Sodegaura, 19 December: 10.5 µg/m³, 1.6× usual Sodegaura, 20 December: 26.5 µg/m³, 4.1× usual Sodegaura, 21 December: 10.4 µg/m³, 1.6× usual Sodegaura, 22 December: 3.1 µg/m³, 0.5× usual Sodegaura, 23 December: 6.0 µg/m³, 0.9× usual Sodegaura, 24 December: 10.1 µg/m³, 1.6× usual Mooka Mooka, 17 December: 12.8 µg/m³, 1.9× usual Mooka, 18 December: 4.8 µg/m³, 0.7× usual Mooka, 19 December: 11.3 µg/m³, 1.7× usual Mooka, 20 December: 26.5 µg/m³, 3.9× usual Mooka, 21 December: 20.0 µg/m³, 2.9× usual Mooka, 22 December: no reading Mooka, 23 December: 8.1 µg/m³, 1.2× usual Mooka, 24 December: 7.6 µg/m³, 1.1× usual Igusa Igusa, 17 December: 11.5 µg/m³, 1.3× usual Igusa, 18 December: 3.4 µg/m³, 0.4× usual Igusa, 19 December: 10.9 µg/m³, 1.2× usual Igusa, 20 December: 26.1 µg/m³, 2.9× usual Igusa, 21 December: 27.2 µg/m³, 3.0× usual Igusa, 22 December: 3.3 µg/m³, 0.4× usual Igusa, 23 December: 11.2 µg/m³, 1.2× usual Igusa, 24 December: 13.3 µg/m³, 1.5× usual Inzai Inzai, 17 December: 14.3 µg/m³, 1.8× usual Inzai, 18 December: 9.3 µg/m³, 1.2× usual Inzai, 19 December: 10.1 µg/m³, 1.3× usual Inzai, 20 December: 25.8 µg/m³, 3.2× usual Inzai, 21 December: 19.1 µg/m³, 2.4× usual Inzai, 22 December: 2.5 µg/m³, 0.3× usual Inzai, 23 December: 7.0 µg/m³, 0.9× usual Inzai, 24 December: 9.0 µg/m³, 1.1× usual Chiba Chiba, 17 December: 14.4 µg/m³, 1.8× usual Chiba, 18 December: 10.3 µg/m³, 1.3× usual Chiba, 19 December: 11.3 µg/m³, 1.4× usual Chiba, 20 December: 25.5 µg/m³, 3.2× usual Chiba, 21 December: 15.4 µg/m³, 1.9× usual Chiba, 22 December: 3.6 µg/m³, 0.5× usual Chiba, 23 December: 6.9 µg/m³, 0.9× usual Chiba, 24 December: 10.1 µg/m³, 1.3× usual Noda Noda, 17 December: no reading Noda, 18 December: 6.2 µg/m³, 0.6× usual Noda, 19 December: 16.9 µg/m³, 1.7× usual Noda, 20 December: 25.4 µg/m³, 2.6× usual Noda, 21 December: 42.2 µg/m³, 4.3× usual Noda, 22 December: 2.2 µg/m³, 0.2× usual Noda, 23 December: 12.3 µg/m³, 1.3× usual Noda, 24 December: 12.0 µg/m³, 1.2× usual Sōka Sōka, 17 December: 13.4 µg/m³, 1.5× usual Sōka, 18 December: 5.5 µg/m³, 0.6× usual Sōka, 19 December: 14.7 µg/m³, 1.7× usual Sōka, 20 December: 22.2 µg/m³, 2.5× usual Sōka, 21 December: 38.7 µg/m³, 4.4× usual Sōka, 22 December: 3.2 µg/m³, 0.4× usual Sōka, 23 December: 9.2 µg/m³, 1.0× usual Sōka, 24 December: 10.6 µg/m³, 1.2× usual Kashiwa Kashiwa, 17 December: 14.8 µg/m³, 1.7× usual Kashiwa, 18 December: 6.5 µg/m³, 0.7× usual Kashiwa, 19 December: 15.2 µg/m³, 1.7× usual Kashiwa, 20 December: 24.6 µg/m³, 2.8× usual Kashiwa, 21 December: 38.4 µg/m³, 4.4× usual Kashiwa, 22 December: 4.0 µg/m³, 0.5× usual Kashiwa, 23 December: 9.8 µg/m³, 1.1× usual Kashiwa, 24 December: 11.9 µg/m³, 1.4× usual Misato, Saitama Misato, Saitama, 17 December: 14.3 µg/m³, 1.3× usual Misato, Saitama, 18 December: 6.0 µg/m³, 0.6× usual Misato, Saitama, 19 December: 15.6 µg/m³, 1.5× usual Misato, Saitama, 20 December: 23.4 µg/m³, 2.2× usual Misato, Saitama, 21 December: 37.9 µg/m³, 3.6× usual Misato, Saitama, 22 December: 3.5 µg/m³, 0.3× usual Misato, Saitama, 23 December: 11.3 µg/m³, 1.1× usual Misato, Saitama, 24 December: 10.3 µg/m³, 1.0× usual Kazo Kazo, 17 December: 12.5 µg/m³, 1.2× usual Kazo, 18 December: 4.4 µg/m³, 0.4× usual Kazo, 19 December: 11.4 µg/m³, 1.1× usual Kazo, 20 December: 21.6 µg/m³, 2.0× usual Kazo, 21 December: 37.1 µg/m³, 3.5× usual Kazo, 22 December: 2.7 µg/m³, 0.3× usual Kazo, 23 December: 10.1 µg/m³, 1.0× usual Kazo, 24 December: 12.8 µg/m³, 1.2× usual Koshigaya Koshigaya, 17 December: 13.2 µg/m³, 1.6× usual Koshigaya, 18 December: 4.5 µg/m³, 0.5× usual Koshigaya, 19 December: 15.0 µg/m³, 1.8× usual Koshigaya, 20 December: 22.1 µg/m³, 2.6× usual Koshigaya, 21 December: 35.9 µg/m³, 4.3× usual Koshigaya, 22 December: 3.1 µg/m³, 0.4× usual Koshigaya, 23 December: 9.6 µg/m³, 1.1× usual Koshigaya, 24 December: 9.5 µg/m³, 1.1× usual Hanyū Hanyū, 17 December: 13.5 µg/m³, 1.7× usual Hanyū, 18 December: 4.8 µg/m³, 0.6× usual Hanyū, 19 December: 11.1 µg/m³, 1.4× usual Hanyū, 20 December: 19.3 µg/m³, 2.4× usual Hanyū, 21 December: 35.0 µg/m³, 4.4× usual Hanyū, 22 December: 3.8 µg/m³, 0.5× usual Hanyū, 23 December: 10.7 µg/m³, 1.3× usual Hanyū, 24 December: 13.7 µg/m³, 1.7× usual Kasukabe Kasukabe, 17 December: 11.8 µg/m³, 1.3× usual Kasukabe, 18 December: 4.5 µg/m³, 0.5× usual Kasukabe, 19 December: 14.0 µg/m³, 1.6× usual Kasukabe, 20 December: 22.3 µg/m³, 2.5× usual Kasukabe, 21 December: 34.5 µg/m³, 3.9× usual Kasukabe, 22 December: 3.3 µg/m³, 0.4× usual Kasukabe, 23 December: 10.6 µg/m³, 1.2× usual Kasukabe, 24 December: 10.7 µg/m³, 1.2× usual Kukichūō Kukichūō, 17 December: 12.6 µg/m³, 1.4× usual Kukichūō, 18 December: 4.8 µg/m³, 0.5× usual Kukichūō, 19 December: 10.6 µg/m³, 1.2× usual Kukichūō, 20 December: 21.0 µg/m³, 2.4× usual Kukichūō, 21 December: 33.9 µg/m³, 3.9× usual Kukichūō, 22 December: 3.1 µg/m³, 0.4× usual Kukichūō, 23 December: 9.3 µg/m³, 1.1× usual Kukichūō, 24 December: 11.6 µg/m³, 1.3× usual Tatebayashi Tatebayashi, 17 December: 11.7 µg/m³, 1.4× usual Tatebayashi, 18 December: 4.6 µg/m³, 0.6× usual Tatebayashi, 19 December: 10.4 µg/m³, 1.3× usual Tatebayashi, 20 December: 18.1 µg/m³, 2.2× usual Tatebayashi, 21 December: 32.1 µg/m³, 4.0× usual Tatebayashi, 22 December: 3.6 µg/m³, 0.4× usual Tatebayashi, 23 December: 9.0 µg/m³, 1.1× usual Tatebayashi, 24 December: 12.5 µg/m³, 1.5× usual Sano Sano, 17 December: 11.3 µg/m³, 1.6× usual Sano, 18 December: 7.6 µg/m³, 1.1× usual Sano, 19 December: 9.9 µg/m³, 1.4× usual Sano, 20 December: 21.2 µg/m³, 3.1× usual Sano, 21 December: 31.9 µg/m³, 4.6× usual Sano, 22 December: 6.7 µg/m³, 1.0× usual Sano, 23 December: 7.8 µg/m³, 1.1× usual Sano, 24 December: 10.4 µg/m³, 1.5× usual Saitama Saitama, 17 December: 11.5 µg/m³, 1.4× usual Saitama, 18 December: 4.0 µg/m³, 0.5× usual Saitama, 19 December: 13.6 µg/m³, 1.6× usual Saitama, 20 December: 20.5 µg/m³, 2.4× usual Saitama, 21 December: 29.9 µg/m³, 3.6× usual Saitama, 22 December: 2.9 µg/m³, 0.3× usual Saitama, 23 December: 10.5 µg/m³, 1.3× usual Saitama, 24 December: 10.8 µg/m³, 1.3× usual Kōnosu Kōnosu, 17 December: 10.7 µg/m³, 1.2× usual Kōnosu, 18 December: 2.8 µg/m³, 0.3× usual Kōnosu, 19 December: 11.1 µg/m³, 1.2× usual Kōnosu, 20 December: 21.9 µg/m³, 2.4× usual Kōnosu, 21 December: 29.5 µg/m³, 3.3× usual Kōnosu, 22 December: 2.6 µg/m³, 0.3× usual Kōnosu, 23 December: 10.8 µg/m³, 1.2× usual Kōnosu, 24 December: 13.2 µg/m³, 1.5× usual Gyōda Gyōda, 17 December: 13.3 µg/m³, 1.3× usual Gyōda, 18 December: 5.0 µg/m³, 0.5× usual Gyōda, 19 December: 13.6 µg/m³, 1.3× usual Gyōda, 20 December: 19.3 µg/m³, 1.9× usual Gyōda, 21 December: 29.3 µg/m³, 2.8× usual Gyōda, 22 December: 4.2 µg/m³, 0.4× usual Gyōda, 23 December: 12.8 µg/m³, 1.2× usual Gyōda, 24 December: 14.5 µg/m³, 1.4× usual Bandō Bandō, 17 December: 11.6 µg/m³, 1.4× usual Bandō, 18 December: 4.4 µg/m³, 0.5× usual Bandō, 19 December: 11.6 µg/m³, 1.4× usual Bandō, 20 December: 21.1 µg/m³, 2.5× usual Bandō, 21 December: 28.7 µg/m³, 3.5× usual Bandō, 22 December: 2.3 µg/m³, 0.3× usual Bandō, 23 December: 10.5 µg/m³, 1.3× usual Bandō, 24 December: 11.3 µg/m³, 1.4× usual Ageo Ageo, 17 December: 11.0 µg/m³, 1.4× usual Ageo, 18 December: 3.1 µg/m³, 0.4× usual Ageo, 19 December: 11.5 µg/m³, 1.4× usual Ageo, 20 December: 24.7 µg/m³, 3.0× usual Ageo, 21 December: 28.3 µg/m³, 3.5× usual Ageo, 22 December: 3.5 µg/m³, 0.4× usual Ageo, 23 December: 10.3 µg/m³, 1.3× usual Ageo, 24 December: 10.2 µg/m³, 1.3× usual Kawaguchi Kawaguchi, 17 December: 12.5 µg/m³, 1.5× usual Kawaguchi, 18 December: 3.8 µg/m³, 0.5× usual Kawaguchi, 19 December: 12.8 µg/m³, 1.5× usual Kawaguchi, 20 December: 18.2 µg/m³, 2.2× usual Kawaguchi, 21 December: 28.2 µg/m³, 3.4× usual Kawaguchi, 22 December: 3.2 µg/m³, 0.4× usual Kawaguchi, 23 December: 9.9 µg/m³, 1.2× usual Kawaguchi, 24 December: 10.8 µg/m³, 1.3× usual Kofu Kofu, 17 December: 13.4 µg/m³, 1.5× usual Kofu, 18 December: 6.5 µg/m³, 0.7× usual Kofu, 19 December: 12.4 µg/m³, 1.4× usual Kofu, 20 December: 15.6 µg/m³, 1.8× usual Kofu, 21 December: 27.2 µg/m³, 3.1× usual Kofu, 22 December: 2.5 µg/m³, 0.3× usual Kofu, 23 December: 7.3 µg/m³, 0.8× usual Kofu, 24 December: 8.4 µg/m³, 1.0× usual Asaka Asaka, 17 December: 11.9 µg/m³, 1.4× usual Asaka, 18 December: 3.8 µg/m³, 0.5× usual Asaka, 19 December: 12.5 µg/m³, 1.5× usual Asaka, 20 December: 18.5 µg/m³, 2.2× usual Asaka, 21 December: 26.8 µg/m³, 3.2× usual Asaka, 22 December: 4.1 µg/m³, 0.5× usual Asaka, 23 December: 11.1 µg/m³, 1.3× usual Asaka, 24 December: 12.0 µg/m³, 1.4× usual Minami-Alps Minami-Alps, 17 December: 10.0 µg/m³, 1.4× usual Minami-Alps, 18 December: 5.1 µg/m³, 0.7× usual Minami-Alps, 19 December: 9.7 µg/m³, 1.4× usual Minami-Alps, 20 December: 17.9 µg/m³, 2.5× usual Minami-Alps, 21 December: 26.7 µg/m³, 3.8× usual Minami-Alps, 22 December: 2.3 µg/m³, 0.3× usual Minami-Alps, 23 December: 6.9 µg/m³, 1.0× usual Minami-Alps, 24 December: 7.7 µg/m³, 1.1× usual Matsudo Matsudo, 17 December: 12.7 µg/m³, 1.7× usual Matsudo, 18 December: 5.3 µg/m³, 0.7× usual Matsudo, 19 December: 12.4 µg/m³, 1.6× usual Matsudo, 20 December: 19.7 µg/m³, 2.6× usual Matsudo, 21 December: 26.3 µg/m³, 3.5× usual Matsudo, 22 December: 2.9 µg/m³, 0.4× usual Matsudo, 23 December: 7.0 µg/m³, 0.9× usual Matsudo, 24 December: 8.1 µg/m³, 1.1× usual Ōta Ōta, 17 December: no reading Ōta, 18 December: no reading Ōta, 19 December: 12.1 µg/m³, 1.5× usual Ōta, 20 December: 21.2 µg/m³, 2.6× usual Ōta, 21 December: 26.0 µg/m³, 3.2× usual Ōta, 22 December: 3.2 µg/m³, 0.4× usual Ōta, 23 December: 10.5 µg/m³, 1.3× usual Ōta, 24 December: 15.0 µg/m³, 1.8× usual Niiza Niiza, 17 December: 11.3 µg/m³, 1.4× usual Niiza, 18 December: 3.3 µg/m³, 0.4× usual Niiza, 19 December: 11.3 µg/m³, 1.4× usual Niiza, 20 December: 19.5 µg/m³, 2.4× usual Niiza, 21 December: 25.4 µg/m³, 3.1× usual Niiza, 22 December: 2.8 µg/m³, 0.3× usual Niiza, 23 December: 9.9 µg/m³, 1.2× usual Niiza, 24 December: 11.1 µg/m³, 1.4× usual 17 Dec 18 19 20 21 22 23 24 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
Toride Ibaraki, Japan 2 21 December 8.0 5.3× Hitachi-Naka Ibaraki, Japan 1 20 December 5.8 5.2× Tsuchiura Ibaraki, Japan 2 21 December 9.6 5.0× Sano Tochigi, Japan 1 21 December 6.9 4.6× Naka Ibaraki, Japan 2 21 December 9.3 4.6× Kimitsu Chiba, Japan 1 20 December 6.6 4.4× Ishioka Ibaraki, Japan 2 21 December 7.8 4.4× Kashiwa Chiba, Japan 1 21 December 8.7 4.4× Sōka Saitama, Japan 1 21 December 8.8 4.4× Hanyū Saitama, Japan 1 21 December 8.0 4.4× Noda Chiba, Japan 2 21 December 9.8 4.3× Koshigaya Saitama, Japan 1 21 December 8.4 4.3× Sodegaura Chiba, Japan 1 20 December 6.4 4.1× Jōsō Ibaraki, Japan 2 21 December 10.0 4.1× Hokota Ibaraki, Japan 2 20 December 7.4 4.0× Ichihara Chiba, Japan 1 20 December 6.8 4.0× Tatebayashi Gunma, Japan 1 21 December 8.1 4.0× Shimo-tsuma Ibaraki, Japan 2 21 December 10.1 4.0× Kasukabe Saitama, Japan 1 21 December 8.8 3.9× Mooka Tochigi, Japan 1 20 December 6.8 3.9× Kisarazu Chiba, Japan 1 20 December 7.2 3.9× Kukichūō Saitama, Japan 1 21 December 8.8 3.9× Sakura Chiba, Japan 1 20 December 7.4 3.8× Minami-Alps Yamanashi, Japan 1 21 December 7.1 3.8× Oyama Tochigi, Japan 2 21 December 9.6 3.7× Kamisu Ibaraki, Japan 1 20 December 7.5 3.7× Misato, Saitama Saitama, Japan 1 21 December 10.6 3.6× Saitama Saitama, Japan 1 21 December 8.4 3.6× Kazo Saitama, Japan 1 21 December 10.6 3.5× Ageo Saitama, Japan 1 21 December 8.1 3.5× Matsudo Chiba, Japan 1 21 December 7.6 3.5× Bandō Ibaraki, Japan 1 21 December 8.3 3.5× Kawaguchi Saitama, Japan 1 21 December 8.4 3.4× Kōnosu Saitama, Japan 1 21 December 9.0 3.3× Yotsukaidō Chiba, Japan 1 20 December 9.1 3.3× Asaka Saitama, Japan 1 21 December 8.3 3.2× Chiba Chiba, Japan 1 20 December 7.9 3.2× Inzai Chiba, Japan 1 20 December 8.0 3.2× Yachimata Chiba, Japan 1 20 December 8.3 3.2× Ōta Gunma, Japan 1 21 December 8.2 3.2× Yachiyo Chiba, Japan 1 20 December 9.3 3.2× Kofu Yamanashi, Japan 1 21 December 8.7 3.1× Chikusei Ibaraki, Japan 2 20 December 11.3 3.1× Kamagaya Chiba, Japan 2 21 December 8.9 3.1× Niiza Saitama, Japan 1 21 December 8.2 3.1× Igusa Saitama, Japan 2 21 December 9.0 3.0× Gyōda Saitama, Japan 1 21 December 10.4 2.8×
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 Japan
Number 15 of 27 episodes in Japan since our records began, by cities reached.
Japan, June and July 2025 508 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, July 2026 172 Japan, November 2023 131 Japan, August 2025 126 Japan, January and February 2025 110 Japan, May 2025 103 Japan, March 2025 92 Japan and South Korea, April 2025 86 Japan, December 2025 47 Bars: cities reached; colour: the level of the episode's highest daily reading. All 27 .
Use this page SmogRank, Japan, December 2025: 47 cities with PM2.5 at twice their usual or more, 20 to 21 December 2025, smogrank.com/episodes/2025-12-japan (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.
