Zao Onsen is one of Japan’s oldest ski and hot spring resorts located right on the border of Yamagata and Miyagi prefectures in Tohoku.
While in summer the resort is famous for the beautiful emerald green pond of the Okama Crater, it are the Juhyo or Ice Monsters that attract loads of primarily Asian tourists every winter.

Juhyo
Juhyo, written as 樹氷 in Japanese are promoted in Tohoku as snow or ice monsters
Indeed the name Ice Monsters is a kind of invented marketing term referring to the special type of fir trees covered with ice that are found in this region only. In February when the “Ice Monsters” are at their peak they resemble grotesque figurines that hold the middle between zombies and giant Yeti’s.

The literal meaning of the two Japanese characters 樹氷 is actually frost covered trees. This Japanese term hints very well to how the “monsters” are created.
In winter Siberian winds crossing the Sea of Japan bring extreme cold moisture over the Tohoku region. When these cold winds hit the fir trees on the north-west slopes of the mountain a kind of hoarfrost is formed on the branches. Hence during the course of the long harsh winter in Tohoku the trees gradually take their monster-like shape.

Apart from Zao Onsen this spectacular phenomenon can also be enjoyed at Mount Hakkoda and Mount Morigoshi further north in Tohoku.
Ski resort
Already in the Edo period the Zao Onsen region was frequented by worshippers and was known for the many volcanic hot springs in the area. However this small mountain village was really put on the map when in 1925 it opened as a ski resort. Ever since it is one of Japan’s leading ski resorts.

Skiers can enjoy a dozen courses, the longest being 10 km, served by a network of 37 ropeways, cable cars and lifts. Despite bad weather and warm conditions the days before I arrived the course and ski slopes were still in remarkably good condition. Many of the ski courses open scenic views of the surrounding mountain ranges and valleys.

Especially the Zangezaka course running through the Ice Monster fields is really worth it.
Igamochi
Don’t leave Zao Onsen without having tried the local specialty Igamochi. They are freshly made sweet rice cakes, topped with yellow flower rice grains and served on a bamboo leave. Inside is the typical red bean paste.

I tried the Igamochi at the cosy coffee shop Sanbe in the winter of 2019. The friendly owner of this cosy place luckily managed to preserve somehow the Japanese charm reminiscent of a long past era. Sadly while doing my research for this article I learned that the coffee shop was severely hit by the devastating typhoon Hagibis late 2019. It seems Sanbe has not re-opened. I do hope the owner finds the courage and means to start again.
Picture perfect conditions are not necessary to visit Zao Onsen
I was in Zao Onsen in late February and it felt almost like spring. After a week of abnormally warm weather with rain the ice monsters in some areas lost partially their shape.
However as you can see on my photos weather was superb the day I was there and to be fair the overall state of the monsters was not as bad as some of the locals and the Zao Onsen tourism agency wanted me to believe when I made an inquiry the day before.

Unless you want to take the same photos of the brochures made during a handful days with perfect conditions just go and enjoy. You will not be disappointed. My recommendation is to keep an eye on the weather forecast much more than the condition of the snow monsters. Fog, heavy snowfall and rain are definitely a no go.
Focus primarily on Asian tourists?
A bit disappointing though was that despite being high season I saw almost no individual (Western) families. Partially this may be related to the fact that almost no English is spoken. Despite being able to express myself in Japanese and even read it a little bit, language issues on the phone, website an inquiry forms at the tourism and trekking agencies stopped me from booking a local guide for one of the heavily hyped snow trekking tours.
Right or wrong I had the impression that the main focus is on the hundreds and hundreds of Asian, primarily Chinese tourists visiting Zao with day package tours. At the crowded Zao ropeway base station it felt more like in Beijing’s Huaibei resort on a sunday rather than an ordinary weekday in the north of Honshū.
Access
Zao Onsen can easily be reached from Yamagata (3 hours by Shinkansen from Tokyo station). From Yamagata station busses bring you on a scenic route in 40 minutes to the resort. The bus time table is available on the website of the Zao Onsen tourism association.
Conclusion
I missed in Zao Onsen somewhat the typical charm and warm hospitality of many other places in Japan, especially for individual travellers and families that do not speak Japanese. Having said that don’t let this withhold you to visit Zao Onsen on a day with nice weather. Skiing or walking amidst the beautiful scenery and Ice Monsters make Zao Onsen a really worthwhile day trip from Yamagata.