SmogRank / Episodes / Japan
Japan, December 2023
For 2 days, from 9 to 10 December 2023, 21 cities in Japan had PM2.5 at least twice their usual for the time of year. The worst reading was Chikusei, Ibaraki, Japan: 44.9 µg/m³ on 9 December, about 3.9× its usual 11.4.
No cause named We have no fire or smoke records for these days, so we only say what the measurements show.
Cities reached 21 in 1 country
Days 2 9 to 10 December 2023
Worst day 10 December 20 cities counted
Furthest above usual 3.9× Chikusei
Day by day
Play 10 December 20 cities at twice their usual or more
Owariasahi Seto Nisshin Nagoya Tajimi Inuyama Toyota Ama Chiryū Tōkai Ichinomiya Kariya Kakamigahara Minokamo Anjō Sekimachi Yatomi Okazaki Gifu Hekinan Handa Hashima Nishio Tokoname Kaizu Kuwana Mizuho Ōgaki Motosu Kaminoma Gamagōri Inabe Yokkaichi Ibi Minamichita Suzuka Shinshiro Toyohashi Tahara Gero Kameyama Tsu Kosai Toba Nagahama Hikone Saikū Matsusaka Ise Youkaichi Iida Hamakita Hamamatsu Kōka Shima Takayama Iwata Iga Ueno-ebisumachi Fukuroi Takashima Kusatsu Kakegawa Kitahama Nabari Ina Ōtsu Kikugawa Shimada Uji Jōyō Kizugawa Kaga Kyoto Fujieda Sugai Komatsu Okaya Nara-shi Tenri Kōtari Yawata Suwa Matsutō Nonoichi Shizuoka Matsumoto Tonami Owase Kashihara-shi Hōryūji Ikoma Kanazawa Kameoka Oyabe Kashiwara Tsubata Toyama Minami-Alps Takaoka Nantan Imizu Namerikawa Kumano Toyonaka Kofu Uozu Himimachi Hashimoto Fuji Hakui Amagasaki Chikuma Maizuru Takarazuka Ueda Yamanashi Nishinomiya Ayabe Nyūzen Fujiyoshida Shingū Sandachō Nanao Nagano Miyazu Numazu Kinokawa Susono Fukuchiyama Kobe Suzaka Izunokuni Iwade Tanba Itoigawa Ōtsuki Shimoda Kyōtango Anamizu Atami Nishiwaki Akashi Minamiashigara Kainan Ono Minato Odawara Tomioka Chichibu Hadano Arida Toyooka Tanabe Nakanojō Jōetsu Gobō Takasaki Ōme Sumoto Minawa Hiratsuka Kodamachō-kodamaminami Aihara Hachiōji Shibukawa Himeji Yorii Atsugi Ebina Hannō Chigasaki Morohongō Ogawamachi Honjō Akishima Ayase Yokota Iruma Minamirinkan Yamato Machida Fujisawa Sakai-nakajima Ikaruga Numata Sayama Sakado Tatsuno Fuchū Higashimurayama Tokorozawa Kodaira Kamakura Higashi-Matsuyama Kumagaya Higashikurume Azamino Igusa Kawagoe Menuma Noborito Aioi Ōta Kiryū Miura Gyōda Niiza Narutochō-mitsuishi Minamiuonuma Kōnosu Yokohama Asaka Yokosuka Kariya Ashikaga Kurihama Anan Ageo Tokushima Tokyo Tatebayashi Saitama Kawaguchi Kukichūō Sano Tottori-shi Bizen Kasukabe Sōka Koshigaya Kimitsu Tateyama Koga Kamojimachō-jōgejima Urayasu Misato, Saitama Matsudo Tochigi Yoshinogawa Bandō Shido Oyama Sodegaura Tsuyama Kanuma Kashiwa Kamagaya Hiragi Imaichi Narashino Ichihara Takamatsu Mima Chiba Toride Kaminokawa Yachiyo Utsunomiya Yotsukaidō Inzai Kurayoshi Mooka Takinomiya Sakura Naka Ajiki Mobara Ōami Yaita Yachimata Narita Tōgane Marugame Ōhara Inashiki Zentsujichó Ishioka Ikedachō Takahashi Kasama Nasukarasuyama Yokoshiba Nasushiobara Niimi Aki Mito Hitachiomiya Omigawa Shikokuchūō Yonago Kashima-shi Aizu-Wakamatsu Hitachi-Naka Nankoku Shirakawa Yasugichō Sakaiminato Shin’ichi Choshi Kochi Hitachi Onomichi Niihama Ino Matsue Kōriyama Mihara Kitaibaraki Saijō Unnan Susaki Imabari Miyoshi Takehara Izumo Iwaki Shinagawa Higashihiroshima Matsuyama Ōdachō-ōda Yae Kure Iyo Gion Minami-Sōma Hiroshima Nakamura Gōtsuchō Uwajima Ōtake Yawatahama Iwakuni Hamada Yanai Noda Shimo-tsuma Kazo Tsuchiura Tamano Jōsō Hokota Higashinozoe Sōsa Sōja Asakuchi Kakogawachō-honmachi Kurashiki Kamisu Fukuyama Kan’onjichō Okayama Kisarazu Ōmihachiman Kasaoka Chikusei 6 Dec 7 8 9 10 11 12 13 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
Chikusei Chikusei, 6 December: 12.8 µg/m³, 1.1× usual Chikusei, 7 December: 13.2 µg/m³, 1.2× usual Chikusei, 8 December: 15.5 µg/m³, 1.4× usual Chikusei, 9 December: 44.9 µg/m³, 3.9× usual Chikusei, 10 December: 28.4 µg/m³, 2.5× usual Chikusei, 11 December: 13.8 µg/m³, 1.2× usual Chikusei, 12 December: 12.5 µg/m³, 1.1× usual Chikusei, 13 December: 6.8 µg/m³, 0.6× usual Kasaoka Kasaoka, 6 December: 16.5 µg/m³, 1.8× usual Kasaoka, 7 December: 16.3 µg/m³, 1.8× usual Kasaoka, 8 December: 23.0 µg/m³, 2.6× usual Kasaoka, 9 December: 28.0 µg/m³, 3.1× usual Kasaoka, 10 December: 35.0 µg/m³, 3.9× usual Kasaoka, 11 December: 17.0 µg/m³, 1.9× usual Kasaoka, 12 December: 5.7 µg/m³, 0.6× usual Kasaoka, 13 December: 6.5 µg/m³, 0.7× usual Sōja Sōja, 6 December: 13.4 µg/m³, 1.6× usual Sōja, 7 December: 15.2 µg/m³, 1.8× usual Sōja, 8 December: 19.4 µg/m³, 2.3× usual Sōja, 9 December: 27.6 µg/m³, 3.3× usual Sōja, 10 December: 25.0 µg/m³, 3.0× usual Sōja, 11 December: 17.3 µg/m³, 2.1× usual Sōja, 12 December: 3.5 µg/m³, 0.4× usual Sōja, 13 December: 4.6 µg/m³, 0.5× usual Jōsō Jōsō, 6 December: 10.0 µg/m³, 0.9× usual Jōsō, 7 December: 9.7 µg/m³, 0.8× usual Jōsō, 8 December: 7.7 µg/m³, 0.7× usual Jōsō, 9 December: 27.1 µg/m³, 2.4× usual Jōsō, 10 December: 32.0 µg/m³, 2.8× usual Jōsō, 11 December: 12.4 µg/m³, 1.1× usual Jōsō, 12 December: 10.4 µg/m³, 0.9× usual Jōsō, 13 December: 4.0 µg/m³, 0.3× usual Shimo-tsuma Shimo-tsuma, 6 December: 12.1 µg/m³, 1.1× usual Shimo-tsuma, 7 December: 12.0 µg/m³, 1.1× usual Shimo-tsuma, 8 December: 8.3 µg/m³, 0.7× usual Shimo-tsuma, 9 December: 25.9 µg/m³, 2.3× usual Shimo-tsuma, 10 December: 26.8 µg/m³, 2.4× usual Shimo-tsuma, 11 December: 12.3 µg/m³, 1.1× usual Shimo-tsuma, 12 December: 8.3 µg/m³, 0.7× usual Shimo-tsuma, 13 December: 4.6 µg/m³, 0.4× usual Kan’onjichō Kan’onjichō, 6 December: 11.9 µg/m³, 1.3× usual Kan’onjichō, 7 December: no reading Kan’onjichō, 8 December: 18.9 µg/m³, 2.0× usual Kan’onjichō, 9 December: 25.8 µg/m³, 2.7× usual Kan’onjichō, 10 December: 32.5 µg/m³, 3.5× usual Kan’onjichō, 11 December: 13.0 µg/m³, 1.4× usual Kan’onjichō, 12 December: 7.1 µg/m³, 0.8× usual Kan’onjichō, 13 December: 6.6 µg/m³, 0.7× usual Noda Noda, 6 December: 9.9 µg/m³, 0.9× usual Noda, 7 December: 11.8 µg/m³, 1.1× usual Noda, 8 December: 7.1 µg/m³, 0.6× usual Noda, 9 December: 25.3 µg/m³, 2.3× usual Noda, 10 December: 24.8 µg/m³, 2.2× usual Noda, 11 December: 13.9 µg/m³, 1.3× usual Noda, 12 December: 14.8 µg/m³, 1.3× usual Noda, 13 December: 1.8 µg/m³, 0.2× usual Kurashiki Kurashiki, 6 December: 15.7 µg/m³, 1.6× usual Kurashiki, 7 December: 15.5 µg/m³, 1.6× usual Kurashiki, 8 December: 18.6 µg/m³, 1.9× usual Kurashiki, 9 December: 24.4 µg/m³, 2.5× usual Kurashiki, 10 December: 30.8 µg/m³, 3.2× usual Kurashiki, 11 December: 18.0 µg/m³, 1.9× usual Kurashiki, 12 December: 5.2 µg/m³, 0.5× usual Kurashiki, 13 December: 4.2 µg/m³, 0.4× usual Fukuyama Fukuyama, 6 December: 11.5 µg/m³, 1.3× usual Fukuyama, 7 December: 16.1 µg/m³, 1.8× usual Fukuyama, 8 December: 23.0 µg/m³, 2.6× usual Fukuyama, 9 December: 23.0 µg/m³, 2.6× usual Fukuyama, 10 December: 30.0 µg/m³, 3.4× usual Fukuyama, 11 December: 16.3 µg/m³, 1.8× usual Fukuyama, 12 December: 4.5 µg/m³, 0.5× usual Fukuyama, 13 December: 5.4 µg/m³, 0.6× usual Asakuchi Asakuchi, 6 December: 13.2 µg/m³, 1.4× usual Asakuchi, 7 December: 13.6 µg/m³, 1.4× usual Asakuchi, 8 December: 19.9 µg/m³, 2.1× usual Asakuchi, 9 December: 23.7 µg/m³, 2.5× usual Asakuchi, 10 December: 29.8 µg/m³, 3.1× usual Asakuchi, 11 December: 16.8 µg/m³, 1.8× usual Asakuchi, 12 December: 5.1 µg/m³, 0.5× usual Asakuchi, 13 December: 4.5 µg/m³, 0.5× usual Kisarazu Kisarazu, 6 December: 9.7 µg/m³, 1.3× usual Kisarazu, 7 December: 7.9 µg/m³, 1.0× usual Kisarazu, 8 December: 8.8 µg/m³, 1.1× usual Kisarazu, 9 December: 10.3 µg/m³, 1.3× usual Kisarazu, 10 December: 28.0 µg/m³, 3.6× usual Kisarazu, 11 December: 15.4 µg/m³, 2.0× usual Kisarazu, 12 December: 9.7 µg/m³, 1.3× usual Kisarazu, 13 December: 5.7 µg/m³, 0.7× usual Tsuchiura Tsuchiura, 6 December: no reading Tsuchiura, 7 December: no reading Tsuchiura, 8 December: 8.0 µg/m³, 0.8× usual Tsuchiura, 9 December: 21.8 µg/m³, 2.1× usual Tsuchiura, 10 December: 27.6 µg/m³, 2.7× usual Tsuchiura, 11 December: 10.3 µg/m³, 1.0× usual Tsuchiura, 12 December: 7.1 µg/m³, 0.7× usual Tsuchiura, 13 December: 4.1 µg/m³, 0.4× usual Kakogawachō-honmachi Kakogawachō-honmachi, 6 December: 15.9 µg/m³, 1.9× usual Kakogawachō-honmachi, 7 December: 15.7 µg/m³, 1.9× usual Kakogawachō-honmachi, 8 December: 21.6 µg/m³, 2.6× usual Kakogawachō-honmachi, 9 December: 20.9 µg/m³, 2.5× usual Kakogawachō-honmachi, 10 December: 26.3 µg/m³, 3.2× usual Kakogawachō-honmachi, 11 December: 11.9 µg/m³, 1.4× usual Kakogawachō-honmachi, 12 December: 5.8 µg/m³, 0.7× usual Kakogawachō-honmachi, 13 December: 3.7 µg/m³, 0.4× usual Okayama Okayama, 6 December: 12.6 µg/m³, 1.7× usual Okayama, 7 December: 12.3 µg/m³, 1.7× usual Okayama, 8 December: 13.9 µg/m³, 1.9× usual Okayama, 9 December: 17.0 µg/m³, 2.3× usual Okayama, 10 December: 25.9 µg/m³, 3.5× usual Okayama, 11 December: 14.9 µg/m³, 2.0× usual Okayama, 12 December: 3.3 µg/m³, 0.4× usual Okayama, 13 December: 3.3 µg/m³, 0.4× usual Higashinozoe Higashinozoe, 6 December: 15.0 µg/m³, 1.7× usual Higashinozoe, 7 December: 14.5 µg/m³, 1.6× usual Higashinozoe, 8 December: 18.5 µg/m³, 2.1× usual Higashinozoe, 9 December: 20.1 µg/m³, 2.3× usual Higashinozoe, 10 December: 25.9 µg/m³, 2.9× usual Higashinozoe, 11 December: 11.9 µg/m³, 1.3× usual Higashinozoe, 12 December: 7.0 µg/m³, 0.8× usual Higashinozoe, 13 December: 3.5 µg/m³, 0.4× usual Hokota Hokota, 6 December: 6.0 µg/m³, 0.7× usual Hokota, 7 December: 8.6 µg/m³, 1.0× usual Hokota, 8 December: 10.2 µg/m³, 1.1× usual Hokota, 9 December: 22.4 µg/m³, 2.5× usual Hokota, 10 December: 25.8 µg/m³, 2.9× usual Hokota, 11 December: 9.1 µg/m³, 1.0× usual Hokota, 12 December: 4.7 µg/m³, 0.5× usual Hokota, 13 December: 5.1 µg/m³, 0.6× usual Sōsa Sōsa, 6 December: 11.1 µg/m³, 1.3× usual Sōsa, 7 December: 9.0 µg/m³, 1.1× usual Sōsa, 8 December: 10.2 µg/m³, 1.2× usual Sōsa, 9 December: 17.6 µg/m³, 2.1× usual Sōsa, 10 December: 25.6 µg/m³, 3.0× usual Sōsa, 11 December: 13.7 µg/m³, 1.6× usual Sōsa, 12 December: 5.7 µg/m³, 0.7× usual Sōsa, 13 December: 4.4 µg/m³, 0.5× usual Tamano Tamano, 6 December: 16.0 µg/m³, 1.7× usual Tamano, 7 December: 15.5 µg/m³, 1.6× usual Tamano, 8 December: 19.4 µg/m³, 2.0× usual Tamano, 9 December: 19.7 µg/m³, 2.1× usual Tamano, 10 December: 25.5 µg/m³, 2.7× usual Tamano, 11 December: 14.9 µg/m³, 1.6× usual Tamano, 12 December: 6.2 µg/m³, 0.6× usual Tamano, 13 December: 3.4 µg/m³, 0.4× usual Kazo Kazo, 6 December: 11.1 µg/m³, 1.1× usual Kazo, 7 December: 11.0 µg/m³, 1.1× usual Kazo, 8 December: 11.3 µg/m³, 1.1× usual Kazo, 9 December: 22.6 µg/m³, 2.2× usual Kazo, 10 December: 25.3 µg/m³, 2.5× usual Kazo, 11 December: 19.5 µg/m³, 1.9× usual Kazo, 12 December: 12.2 µg/m³, 1.2× usual Kazo, 13 December: 4.3 µg/m³, 0.4× usual Ōmihachiman Ōmihachiman, 6 December: 12.7 µg/m³, 1.9× usual Ōmihachiman, 7 December: 13.1 µg/m³, 2.0× usual Ōmihachiman, 8 December: 19.8 µg/m³, 3.0× usual Ōmihachiman, 9 December: 20.7 µg/m³, 3.1× usual Ōmihachiman, 10 December: 25.2 µg/m³, 3.8× usual Ōmihachiman, 11 December: 9.8 µg/m³, 1.5× usual Ōmihachiman, 12 December: no reading Ōmihachiman, 13 December: no reading Kamisu Kamisu, 6 December: 10.5 µg/m³, 1.4× usual Kamisu, 7 December: 7.5 µg/m³, 1.0× usual Kamisu, 8 December: 9.7 µg/m³, 1.3× usual Kamisu, 9 December: 21.0 µg/m³, 2.7× usual Kamisu, 10 December: 25.1 µg/m³, 3.3× usual Kamisu, 11 December: 14.1 µg/m³, 1.8× usual Kamisu, 12 December: 4.9 µg/m³, 0.6× usual Kamisu, 13 December: 6.4 µg/m³, 0.8× usual 6 Dec 7 8 9 10 11 12 13 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
Chikusei Ibaraki, Japan 2 9 December 11.4 3.9× Kasaoka Okayama, Japan 1 10 December 9.0 3.9× Ōmihachiman Shiga, Japan 1 10 December 6.7 3.8× Kisarazu Chiba, Japan 1 10 December 7.7 3.6× Okayama Okayama, Japan 1 10 December 7.4 3.5× Kan’onjichō Kagawa, Japan 1 10 December 9.4 3.5× Fukuyama Hiroshima, Japan 1 10 December 8.9 3.4× Sōja Okayama, Japan 1 9 December 8.4 3.3× Kamisu Ibaraki, Japan 1 10 December 7.7 3.3× Kurashiki Okayama, Japan 1 10 December 9.6 3.2× Kakogawachō-honmachi Hyōgo, Japan 1 10 December 8.3 3.2× Asakuchi Okayama, Japan 1 10 December 9.5 3.1× Sōsa Chiba, Japan 1 10 December 8.4 3.0× Higashinozoe Hyōgo, Japan 1 10 December 8.9 2.9× Hokota Ibaraki, Japan 1 10 December 9.0 2.9× Jōsō Ibaraki, Japan 2 10 December 11.5 2.8× Tsuchiura Ibaraki, Japan 1 10 December 10.2 2.7× Tamano Okayama, Japan 1 10 December 9.6 2.7× Kazo Saitama, Japan 1 10 December 10.1 2.5× Shimo-tsuma Ibaraki, Japan 2 10 December 11.3 2.4× Noda Chiba, Japan 1 9 December 11.1 2.3×
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 Japan
Number 2 of 5 episodes in Japan since our records began, by cities reached.
Bars: cities reached; colour: the level of the episode's highest daily reading.
Use this page SmogRank, Japan, December 2023: 21 cities with PM2.5 at twice their usual or more, 9 to 10 December 2023, smogrank.com/episodes/2023-12-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.
