In the depths of winter, the forests of the Zao Mountains become almost surreal. The tree no longer looks like a tree. They rise in bulky, twisted shapes, covered with thick layers of white ice, standing silently against the wind. Tourists call them Japan’s “snow monsters.” In Japanese, they are called “juhyo,” which literally means “ice tree.”At first glance, they look mysterious. In fact, they are the result of precise and fragile atmospheric processes. Scientists warn that the conditions required to create them are becoming increasingly difficult to maintain.
The science behind Japan’s snow monster
These structures occur mainly on Mount Zao Jizo, which straddles Miyagi and Yamagata prefectures. according to Researcher at Yamagata University, tree ice When strong monsoon winds blow from the Sea of Japan, clouds filled with supercooled water droplets form. When these water droplets collide with conifers, especially native Aomori fir trees, they freeze instantly.Over days and weeks, rime ice builds up. The ice thickens on the windward side of the trees, gradually forming a ridge that locals call “shrimp tails.” As more ice piles up, the trees lose their natural contours and take on giant shapes, earning them the nickname “snow monsters.”according to Local tourist office and Zao RopewayThe best time to observe this phenomenon is usually from mid-January to early March, when temperatures are consistently below freezing and winds are strong enough to sustain ice formation.
From Hokkaido to Ishikawa: The extent of Japan’s disappearing snow monsters
Many visitors don’t realize these snow monsters were once more common.Professor Fumitaka Yanagisawa, Emeritus Professor Yamagata University Zao Hyomon Volcano Research Institutespent years studying historical photos and climbing records. According to his research, tree ice formations have been recorded not only in Zao but also throughout Hokkaido and as far south as Ishikawa Prefecture. Historical records indicate that they extended 50 to 60 kilometers inland from the Sea of Japan until around the mid-20th century.One of the earliest confirmed photographs dates back to 1921 and was taken by a mountaineering club at Zao Keio University. Another rare image from 1923 was discovered in Toyama Prefecture. Additional documentation from Nagano and Niigata prefectures further supports the idea that tree ice once covered a wider geographical range.Today, however, the most important ruins are concentrated in three places: Mount Zao, Mount Hakkoda, and Mount Moriyoshi. Among them, Zao Wou-Ki remains the largest and most iconic.
What rising temperatures mean for Japan’s snow monsters
The reason for their retreat is not folklore but physics.According to Professor Yanagisawa’s climate analysis, rising winter temperatures and subtle changes in wind patterns are reducing the frequency of ideal tree ice-forming conditions. Even a small increase in average winter temperatures could shorten the freezing period, reduce the amount of supercooled cloud water, and harm the health of the Aomori fir forests that support the ground.Data from the Japan Meteorological Agency shows that winter temperatures in northern Japan have gradually warmed in recent decades. While researchers are unable to predict that tree ice will disappear entirely, projections suggest that without significant climate stabilization, the density and extent of tree ice may continue to shrink by the end of the century.In this sense, the Yeti is more than just a tourist attraction. They are clear signs of environmental change.
The cultural appeal of the frozen giant
The emotional bond runs deeper than science. People who live in Yamagata and Miyagi remember the snow monsters, winter festivals and nighttime excursions along the ropeway from their childhood.Their ghostly shapes are naturally reminiscent of Japan’s long history of folk tales. Shinto believers believe that gods or spirits live in nature. The strange shapes that appear in winter often remind visitors of yokai in Japanese stories. Yuki-onna Yuki-onna is one of them. Her story dates back to the Muromachi period.The fact that hoarfrost looks like these myths adds to their mystique, even though they are not directly from the myths. British naturalist Richard Gordon Smith and other early Western observers wrote about winter folklore in books such as Ancient Japanese Tales and Folklore, saying that snow spirits haunted the mountain landscape. These images still have an impact today.
Currently, Zao’s snow monster still appears every winter
Thousands of people travel to Zao every year to see the glowing ice formations under the night sky. Skiers weave between the frozen towers and photographers capture the strange shapes.But scientists still keep a close eye on the forest. The main goals are to study the weather, focus on forest health, and figure out how long-term warming may change mountain ecosystems in northern Japan.The snow monster is still there. They rise again every winter when the winds are cold enough and the clouds are thick enough.But their future depends on a fragile balance of time, temperature and wind. Many in Zao understand that such equations are becoming increasingly difficult to balance.
