SmogRank / Episodes / Japan
Chiba and Ibaraki, Japan, August 2025
For 2 days, from 30 to 31 August 2025, 14 cities in Japan had PM2.5 at least twice their usual for the time of year. The worst reading was Kamisu, Ibaraki, Japan: 29.7 µg/m³ on 30 August, about 3.6× its usual 8.2.
No cause named We have no fire or smoke records for these days, so we only say what the measurements show.
Cities reached 14 in 1 country
Days 2 30 to 31 August 2025
Worst day 30 August 10 cities counted
Furthest above usual 4.9× Ōhara
Day by day
Play 30 August 10 cities at twice their usual or more
Matsudo Tokyo Sōka Kawaguchi Misato, Saitama Koshigaya Kamagaya Kashiwa Asaka Noda Saitama Noborito Niiza Kasukabe Azamino Higashikurume Yokohama Toride Kisarazu Kodaira Fuchū Ageo Sodegaura Yotsukaidō Kimitsu Higashimurayama Jōsō Tokorozawa Inzai Bandō Kawagoe Kukichūō Machida Minamirinkan Yamato Ajiki Sayama Yokota Akishima Yokosuka Igusa Iruma Kazo Kamakura Ayase Kōnosu Kurihama Fujisawa Koga Hachiōji Yachimata Sakado Narita Shimo-tsuma Aihara Atsugi Higashi-Matsuyama Hannō Ebina Minawa Hanyū Chigasaki Inashiki Tōgane Morohongō Gyōda Ōme Miura Oyama Hiratsuka Kumagaya Tatebayashi Chikusei Ogawamachi Ishioka Sano Yokoshiba Minamibōsō Hadano Menuma Tochigi Sawara Tateyama Sōsa Ashikaga Kaminokawa Katsuura Yorii Mooka Odawara Chichibu Sakai-nakajima Minamiashigara Omigawa Kasama Honjō Kodamachō-kodamaminami Kiryū Kanuma Utsunomiya Mito Gotemba Atami Hitachi-Naka Nasukarasuyama Imaichi Hitachiomiya Susono Fujiyoshida Tomioka Izunokuni Yaita Yamanashi Numazu Shibukawa Numata Hitachi Kofu Fuji Fujinomiya Nasushiobara Nakanojō Shimoda Minami-Alps Kitaibaraki Saku Shirakawa Shizuoka Minamiuonuma Ueda Iwaki Suwa Fujieda Suzaka Kōriyama Aizu-Wakamatsu Okaya Shimada Ina Nagano Chikuma Matsumoto Kikugawa Nagaoka Iida Kakegawa Fukuroi Jōetsu Fukushima Iwata Shirone Niitsu-honchō Hamakita Yonezawa Minami-Sōma Maki Kameda-honchō Shibata Hamamatsu Niigata Sōma Itoigawa Nagai Shiroishi Shinshiro Kakuda Kosai Gero Takayama Toyohashi Iwanuma Nyūzen Uozu Toki Tajimi Gamagōri Toyota Sado Tahara Okazaki Seto Kani Toyama Minokamo Nisshin Owariasahi Anjō Chiryū Nishio Inuyama Imizu Sekimachi Kariya Hekinan Nagoya Kakamigahara Tōkai Takaoka Minamichita Handa Tonami Ichinomiya Himimachi Ama Gifu Tokoname Kaminoma Oyabe Nanao Hashima Mizuho Kuwana Toba Ōgaki Kaizu Tsubata Hakui Ibi Shima Yokkaichi Anamizu Inabe Nonoichi Kanazawa Suzuka Ono Ise Matsutō Saikū Tsu Komatsu Matsusaka Kameyama Kaga Nagahama Hikone Fukui-shi Sabae Youkaichi Mikuni Kōka Tsuruga Ōmihachiman Iga Ueno-ebisumachi Takashima Nabari Kusatsu Kitahama Owase Ōtsu Obama Kizugawa Uji Jōyō Kumano Kyoto Sugai Tenri Nara-shi Kōtari Kashihara-shi Yawata Hōryūji Kashiwara Ikoma Hirakata Takatsuki Kameoka Shingū Yao Higashiosaka Nantan Habikino Tondabayashichō Yono Sayama Kawachi-Nagano Hashimoto Osaka Toyonaka Maizuru Sakai Amagasaki Izumi Takarazuka Ayabe Nishinomiya Kishiwada Miyazu Kinokawa Sandachō Izumisano Fukuchiyama Iwade Kobe Sennan Kyōtango Tanba Kainan Tanabe Nishiwaki Minato Akashi Arida Gobō Ōtsuki Tsuchiura Naka Yachiyo Kamisu Kashima-shi Hokota Chiba Urayasu Narashino Sakura Mobara Ichihara Ōhara 27 Aug 28 29 30 31 1 Sep 2 3 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
Kamisu Kamisu, 27 August: 8.4 µg/m³, 1.0× usual Kamisu, 28 August: 9.4 µg/m³, 1.1× usual Kamisu, 29 August: 9.2 µg/m³, 1.1× usual Kamisu, 30 August: 29.7 µg/m³, 3.6× usual Kamisu, 31 August: 21.8 µg/m³, 2.7× usual Kamisu, 1 September: 10.3 µg/m³, 1.3× usual Kamisu, 2 September: 5.9 µg/m³, 0.7× usual Kamisu, 3 September: 10.1 µg/m³, 1.2× usual Mobara Mobara, 27 August: 9.4 µg/m³, 1.6× usual Mobara, 28 August: 7.5 µg/m³, 1.3× usual Mobara, 29 August: 9.5 µg/m³, 1.6× usual Mobara, 30 August: 27.7 µg/m³, 4.6× usual Mobara, 31 August: 19.5 µg/m³, 3.3× usual Mobara, 1 September: 9.1 µg/m³, 1.5× usual Mobara, 2 September: 4.0 µg/m³, 0.7× usual Mobara, 3 September: 5.6 µg/m³, 0.9× usual Chiba Chiba, 27 August: 10.4 µg/m³, 1.5× usual Chiba, 28 August: 8.4 µg/m³, 1.2× usual Chiba, 29 August: 13.1 µg/m³, 1.9× usual Chiba, 30 August: 27.1 µg/m³, 3.9× usual Chiba, 31 August: 20.1 µg/m³, 2.9× usual Chiba, 1 September: 11.6 µg/m³, 1.7× usual Chiba, 2 September: 6.0 µg/m³, 0.9× usual Chiba, 3 September: 8.4 µg/m³, 1.2× usual Ōhara Ōhara, 27 August: 5.5 µg/m³, 1.0× usual Ōhara, 28 August: 7.0 µg/m³, 1.3× usual Ōhara, 29 August: 7.8 µg/m³, 1.4× usual Ōhara, 30 August: 26.9 µg/m³, 4.9× usual Ōhara, 31 August: 19.8 µg/m³, 3.6× usual Ōhara, 1 September: 7.1 µg/m³, 1.3× usual Ōhara, 2 September: 3.1 µg/m³, 0.6× usual Ōhara, 3 September: 4.6 µg/m³, 0.8× usual Yachiyo Yachiyo, 27 August: 9.5 µg/m³, 1.3× usual Yachiyo, 28 August: 7.6 µg/m³, 1.0× usual Yachiyo, 29 August: 12.2 µg/m³, 1.7× usual Yachiyo, 30 August: 26.6 µg/m³, 3.6× usual Yachiyo, 31 August: 20.3 µg/m³, 2.8× usual Yachiyo, 1 September: 11.5 µg/m³, 1.6× usual Yachiyo, 2 September: 4.8 µg/m³, 0.7× usual Yachiyo, 3 September: 7.9 µg/m³, 1.1× usual Ichihara Ichihara, 27 August: 8.2 µg/m³, 1.5× usual Ichihara, 28 August: 8.2 µg/m³, 1.5× usual Ichihara, 29 August: 11.6 µg/m³, 2.1× usual Ichihara, 30 August: 26.3 µg/m³, 4.7× usual Ichihara, 31 August: 19.7 µg/m³, 3.5× usual Ichihara, 1 September: 9.5 µg/m³, 1.7× usual Ichihara, 2 September: 3.7 µg/m³, 0.7× usual Ichihara, 3 September: 5.8 µg/m³, 1.0× usual Kashima-shi Kashima-shi, 27 August: 8.4 µg/m³, 1.2× usual Kashima-shi, 28 August: 8.0 µg/m³, 1.1× usual Kashima-shi, 29 August: 8.1 µg/m³, 1.1× usual Kashima-shi, 30 August: 26.2 µg/m³, 3.6× usual Kashima-shi, 31 August: 20.5 µg/m³, 2.8× usual Kashima-shi, 1 September: 10.8 µg/m³, 1.5× usual Kashima-shi, 2 September: 5.5 µg/m³, 0.8× usual Kashima-shi, 3 September: 9.3 µg/m³, 1.3× usual Sakura Sakura, 27 August: 10.4 µg/m³, 1.7× usual Sakura, 28 August: 8.5 µg/m³, 1.4× usual Sakura, 29 August: 10.8 µg/m³, 1.7× usual Sakura, 30 August: 25.6 µg/m³, 4.1× usual Sakura, 31 August: 21.7 µg/m³, 3.5× usual Sakura, 1 September: 12.1 µg/m³, 2.0× usual Sakura, 2 September: 5.0 µg/m³, 0.8× usual Sakura, 3 September: 9.3 µg/m³, 1.5× usual Urayasu Urayasu, 27 August: 9.9 µg/m³, 1.5× usual Urayasu, 28 August: 8.3 µg/m³, 1.3× usual Urayasu, 29 August: 12.7 µg/m³, 2.0× usual Urayasu, 30 August: 25.2 µg/m³, 3.9× usual Urayasu, 31 August: 18.3 µg/m³, 2.9× usual Urayasu, 1 September: 10.5 µg/m³, 1.6× usual Urayasu, 2 September: 4.7 µg/m³, 0.7× usual Urayasu, 3 September: 7.0 µg/m³, 1.1× usual Narashino Narashino, 27 August: 9.5 µg/m³, 1.6× usual Narashino, 28 August: 7.8 µg/m³, 1.3× usual Narashino, 29 August: 11.5 µg/m³, 1.9× usual Narashino, 30 August: 25.1 µg/m³, 4.1× usual Narashino, 31 August: 19.5 µg/m³, 3.2× usual Narashino, 1 September: 11.1 µg/m³, 1.8× usual Narashino, 2 September: 5.9 µg/m³, 1.0× usual Narashino, 3 September: 6.8 µg/m³, 1.1× usual Tsuchiura Tsuchiura, 27 August: 12.0 µg/m³, 1.3× usual Tsuchiura, 28 August: 8.0 µg/m³, 0.9× usual Tsuchiura, 29 August: 14.5 µg/m³, 1.5× usual Tsuchiura, 30 August: 24.2 µg/m³, 2.6× usual Tsuchiura, 31 August: 27.8 µg/m³, 3.0× usual Tsuchiura, 1 September: 15.8 µg/m³, 1.7× usual Tsuchiura, 2 September: 6.8 µg/m³, 0.7× usual Tsuchiura, 3 September: 16.6 µg/m³, 1.8× usual Ōtsuki Ōtsuki, 27 August: 23.4 µg/m³, 2.1× usual Ōtsuki, 28 August: 22.0 µg/m³, 1.9× usual Ōtsuki, 29 August: 18.6 µg/m³, 1.6× usual Ōtsuki, 30 August: 23.5 µg/m³, 2.1× usual Ōtsuki, 31 August: 26.5 µg/m³, 2.3× usual Ōtsuki, 1 September: 23.4 µg/m³, 2.1× usual Ōtsuki, 2 September: 14.3 µg/m³, 1.3× usual Ōtsuki, 3 September: 14.9 µg/m³, 1.3× usual Hokota Hokota, 27 August: 9.8 µg/m³, 1.5× usual Hokota, 28 August: 8.1 µg/m³, 1.2× usual Hokota, 29 August: 7.7 µg/m³, 1.2× usual Hokota, 30 August: 21.5 µg/m³, 3.3× usual Hokota, 31 August: 25.9 µg/m³, 3.9× usual Hokota, 1 September: 14.3 µg/m³, 2.2× usual Hokota, 2 September: 6.3 µg/m³, 1.0× usual Hokota, 3 September: 10.0 µg/m³, 1.5× usual Naka Naka, 27 August: 12.0 µg/m³, 1.5× usual Naka, 28 August: 9.0 µg/m³, 1.2× usual Naka, 29 August: 13.9 µg/m³, 1.8× usual Naka, 30 August: 22.8 µg/m³, 2.9× usual Naka, 31 August: 25.5 µg/m³, 3.3× usual Naka, 1 September: 15.0 µg/m³, 1.9× usual Naka, 2 September: 6.7 µg/m³, 0.9× usual Naka, 3 September: 14.3 µg/m³, 1.8× usual 27 Aug 28 29 30 31 1 Sep 2 3 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
Ōhara Chiba, Japan 1 30 August 5.5 4.9× Ichihara Chiba, Japan 1 30 August 5.6 4.7× Mobara Chiba, Japan 1 30 August 6.0 4.6× Sakura Chiba, Japan 1 30 August 6.2 4.1× Narashino Chiba, Japan 1 30 August 6.1 4.1× Urayasu Chiba, Japan 1 30 August 6.4 3.9× Chiba Chiba, Japan 1 30 August 6.9 3.9× Hokota Ibaraki, Japan 1 31 August 6.6 3.9× Yachiyo Chiba, Japan 1 30 August 7.3 3.6× Kashima-shi Ibaraki, Japan 1 30 August 7.2 3.6× Kamisu Ibaraki, Japan 1 30 August 8.2 3.6× Naka Ibaraki, Japan 1 31 August 7.8 3.3× Tsuchiura Ibaraki, Japan 1 31 August 9.4 3.0× Ōtsuki Yamanashi, Japan 1 31 August 11.4 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 23 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 Chiba and Ibaraki, Japan, August 2025 14 Bars: cities reached; colour: the level of the episode's highest daily reading. All 27 .
Use this page SmogRank, Chiba and Ibaraki, Japan, August 2025: 14 cities with PM2.5 at twice their usual or more, 30 to 31 August 2025, smogrank.com/episodes/2025-08-chiba-and-ibaraki-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.
