SmogRank / Episodes / Japan
Japan, 9 to 10 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 Tamano Tsuchiura Jōsō Hokota Higashinozoe Sōja Sōsa Asakuchi Kakogawachō-honmachi Kurashiki Kamisu Fukuyama Okayama Kan’onjichō 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 Chikusei, 7 December: 13.2 µg/m³ Chikusei, 8 December: 15.5 µg/m³ Chikusei, 9 December: 44.9 µg/m³, 3.9× its usual 11.4 Chikusei, 10 December: 28.4 µg/m³, 2.4× its usual 11.6 Chikusei, 11 December: 13.8 µg/m³ Chikusei, 12 December: 12.5 µg/m³ Chikusei, 13 December: 6.8 µg/m³ Jōsō Jōsō, 6 December: 10.0 µg/m³ Jōsō, 7 December: 9.7 µg/m³ Jōsō, 8 December: 7.7 µg/m³ Jōsō, 9 December: 27.1 µg/m³, 2.5× its usual 10.9 Jōsō, 10 December: 32.0 µg/m³, 2.8× its usual 11.5 Jōsō, 11 December: 12.4 µg/m³ Jōsō, 12 December: 10.4 µg/m³ Jōsō, 13 December: 4.0 µg/m³ Shimo-tsuma Shimo-tsuma, 6 December: 12.1 µg/m³ Shimo-tsuma, 7 December: 12.0 µg/m³ Shimo-tsuma, 8 December: 8.3 µg/m³ Shimo-tsuma, 9 December: 25.9 µg/m³, 2.3× its usual 11.2 Shimo-tsuma, 10 December: 26.8 µg/m³, 2.4× its usual 11.3 Shimo-tsuma, 11 December: 12.3 µg/m³ Shimo-tsuma, 12 December: 8.3 µg/m³ Shimo-tsuma, 13 December: 4.6 µg/m³ Noda Noda, 6 December: 9.9 µg/m³ Noda, 7 December: 11.8 µg/m³ Noda, 8 December: 7.1 µg/m³ Noda, 9 December: 25.3 µg/m³, 2.3× its usual 11.1 Noda, 10 December: 24.8 µg/m³ Noda, 11 December: 13.9 µg/m³ Noda, 12 December: 14.8 µg/m³ Noda, 13 December: 1.8 µg/m³ Kasaoka Kasaoka, 6 December: 16.5 µg/m³ Kasaoka, 7 December: 16.3 µg/m³ Kasaoka, 8 December: 23.0 µg/m³ Kasaoka, 9 December: 28.0 µg/m³ Kasaoka, 10 December: 35.0 µg/m³, 3.9× its usual 9.0 Kasaoka, 11 December: 17.0 µg/m³ Kasaoka, 12 December: 5.7 µg/m³ Kasaoka, 13 December: 6.5 µg/m³ Kan’onjichō Kan’onjichō, 6 December: 11.9 µg/m³ Kan’onjichō, 7 December: no reading Kan’onjichō, 8 December: 18.9 µg/m³ Kan’onjichō, 9 December: 25.8 µg/m³ Kan’onjichō, 10 December: 32.5 µg/m³, 3.5× its usual 9.4 Kan’onjichō, 11 December: 13.0 µg/m³ Kan’onjichō, 12 December: 7.1 µg/m³ Kan’onjichō, 13 December: 6.6 µg/m³ Kurashiki Kurashiki, 6 December: 15.7 µg/m³ Kurashiki, 7 December: 15.5 µg/m³ Kurashiki, 8 December: 18.6 µg/m³ Kurashiki, 9 December: 24.4 µg/m³ Kurashiki, 10 December: 30.8 µg/m³, 3.2× its usual 9.6 Kurashiki, 11 December: 18.0 µg/m³ Kurashiki, 12 December: 5.2 µg/m³ Kurashiki, 13 December: 4.2 µg/m³ Fukuyama Fukuyama, 6 December: 11.5 µg/m³ Fukuyama, 7 December: 16.1 µg/m³ Fukuyama, 8 December: 23.0 µg/m³ Fukuyama, 9 December: 23.0 µg/m³ Fukuyama, 10 December: 30.0 µg/m³, 3.4× its usual 8.9 Fukuyama, 11 December: 16.3 µg/m³ Fukuyama, 12 December: 4.5 µg/m³ Fukuyama, 13 December: 5.4 µg/m³ Asakuchi Asakuchi, 6 December: 13.2 µg/m³ Asakuchi, 7 December: 13.6 µg/m³ Asakuchi, 8 December: 19.9 µg/m³ Asakuchi, 9 December: 23.7 µg/m³ Asakuchi, 10 December: 29.8 µg/m³, 3.1× its usual 9.5 Asakuchi, 11 December: 16.8 µg/m³ Asakuchi, 12 December: 5.1 µg/m³ Asakuchi, 13 December: 4.5 µg/m³ Kisarazu Kisarazu, 6 December: 9.7 µg/m³ Kisarazu, 7 December: 7.9 µg/m³ Kisarazu, 8 December: 8.8 µg/m³ Kisarazu, 9 December: 10.3 µg/m³ Kisarazu, 10 December: 28.0 µg/m³, 3.6× its usual 7.7 Kisarazu, 11 December: 15.4 µg/m³ Kisarazu, 12 December: 9.7 µg/m³ Kisarazu, 13 December: 5.7 µg/m³ Tsuchiura Tsuchiura, 6 December: no reading Tsuchiura, 7 December: no reading Tsuchiura, 8 December: 8.0 µg/m³ Tsuchiura, 9 December: 21.8 µg/m³ Tsuchiura, 10 December: 27.6 µg/m³, 2.7× its usual 10.2 Tsuchiura, 11 December: 10.3 µg/m³ Tsuchiura, 12 December: 7.1 µg/m³ Tsuchiura, 13 December: 4.1 µg/m³ Kakogawachō-honmachi Kakogawachō-honmachi, 6 December: 15.9 µg/m³ Kakogawachō-honmachi, 7 December: 15.7 µg/m³ Kakogawachō-honmachi, 8 December: 21.6 µg/m³ Kakogawachō-honmachi, 9 December: 20.9 µg/m³ Kakogawachō-honmachi, 10 December: 26.3 µg/m³, 3.2× its usual 8.3 Kakogawachō-honmachi, 11 December: 11.9 µg/m³ Kakogawachō-honmachi, 12 December: 5.8 µg/m³ Kakogawachō-honmachi, 13 December: 3.7 µg/m³ Okayama Okayama, 6 December: 12.6 µg/m³ Okayama, 7 December: 12.3 µg/m³ Okayama, 8 December: 13.9 µg/m³ Okayama, 9 December: 17.0 µg/m³ Okayama, 10 December: 25.9 µg/m³, 3.5× its usual 7.4 Okayama, 11 December: 14.9 µg/m³ Okayama, 12 December: 3.3 µg/m³ Okayama, 13 December: 3.3 µg/m³ Higashinozoe Higashinozoe, 6 December: 15.0 µg/m³ Higashinozoe, 7 December: 14.5 µg/m³ Higashinozoe, 8 December: 18.5 µg/m³ Higashinozoe, 9 December: 20.1 µg/m³ Higashinozoe, 10 December: 25.9 µg/m³, 2.9× its usual 8.9 Higashinozoe, 11 December: 11.9 µg/m³ Higashinozoe, 12 December: 7.0 µg/m³ Higashinozoe, 13 December: 3.5 µg/m³ Hokota Hokota, 6 December: 6.0 µg/m³ Hokota, 7 December: 8.6 µg/m³ Hokota, 8 December: 10.2 µg/m³ Hokota, 9 December: 22.4 µg/m³ Hokota, 10 December: 25.8 µg/m³, 2.9× its usual 9.0 Hokota, 11 December: 9.1 µg/m³ Hokota, 12 December: 4.7 µg/m³ Hokota, 13 December: 5.1 µg/m³ Sōsa Sōsa, 6 December: 11.1 µg/m³ Sōsa, 7 December: 9.0 µg/m³ Sōsa, 8 December: 10.2 µg/m³ Sōsa, 9 December: 17.6 µg/m³ Sōsa, 10 December: 25.6 µg/m³, 3.0× its usual 8.4 Sōsa, 11 December: 13.7 µg/m³ Sōsa, 12 December: 5.7 µg/m³ Sōsa, 13 December: 4.4 µg/m³ Tamano Tamano, 6 December: 16.0 µg/m³ Tamano, 7 December: 15.5 µg/m³ Tamano, 8 December: 19.4 µg/m³ Tamano, 9 December: 19.7 µg/m³ Tamano, 10 December: 25.5 µg/m³, 2.7× its usual 9.6 Tamano, 11 December: 14.9 µg/m³ Tamano, 12 December: 6.2 µg/m³ Tamano, 13 December: 3.4 µg/m³ Kazo Kazo, 6 December: 11.1 µg/m³ Kazo, 7 December: 11.0 µg/m³ Kazo, 8 December: 11.3 µg/m³ Kazo, 9 December: 22.6 µg/m³ Kazo, 10 December: 25.3 µg/m³, 2.5× its usual 10.1 Kazo, 11 December: 19.5 µg/m³ Kazo, 12 December: 12.2 µg/m³ Kazo, 13 December: 4.3 µg/m³ Ōmihachiman Ōmihachiman, 6 December: 12.7 µg/m³ Ōmihachiman, 7 December: 13.1 µg/m³ Ōmihachiman, 8 December: 19.8 µg/m³ Ōmihachiman, 9 December: 20.7 µg/m³ Ōmihachiman, 10 December: 25.2 µg/m³, 3.8× its usual 6.7 Ōmihachiman, 11 December: 9.8 µg/m³ Ōmihachiman, 12 December: no reading Ōmihachiman, 13 December: no reading Kamisu Kamisu, 6 December: 10.5 µg/m³ Kamisu, 7 December: 7.5 µg/m³ Kamisu, 8 December: 9.7 µg/m³ Kamisu, 9 December: 21.0 µg/m³ Kamisu, 10 December: 25.1 µg/m³, 3.3× its usual 7.7 Kamisu, 11 December: 14.1 µg/m³ Kamisu, 12 December: 4.9 µg/m³ Kamisu, 13 December: 6.4 µg/m³ Sōja Sōja, 6 December: 13.4 µg/m³ Sōja, 7 December: 15.2 µg/m³ Sōja, 8 December: 19.4 µg/m³ Sōja, 9 December: 27.6 µg/m³ Sōja, 10 December: 25.0 µg/m³, 3.0× its usual 8.4 Sōja, 11 December: 17.3 µg/m³ Sōja, 12 December: 3.5 µg/m³ Sōja, 13 December: 4.6 µg/m³ 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× Kan’onjichō Kagawa, Japan 1 10 December 9.4 3.5× Okayama Okayama, Japan 1 10 December 7.4 3.5× Fukuyama Hiroshima, Japan 1 10 December 8.9 3.4× 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× Sōja Okayama, 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, 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 Japan
Number 27 of 39 episodes in 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 Japan, November 2023 131 Japan, 4 to 5 August 2025 126 Japan, January and February 2025 110 Japan, May 2025 103 Japan, March 2025 92 Japan, 9 to 10 December 2023 21 Bars: cities reached; colour: the level of the episode's highest daily reading. All 39 .
Use this page SmogRank, Japan, 9 to 10 December 2023: 21 cities with PM2.5 at twice their usual or more, 9 to 10 December 2023, smogrank.com/episodes/2023-12-09-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.
