According to the Köppen-Geiger classification, central Hokkaido is Dfb - a snow climate that is fully humid with warm summers.

Horoka Tomamu is close to the 43rd parallel north, the same latitude as the south of France and New York, however Hokkaido's climate is influenced by the cold Oyashio Ocean Current that brings subarctic conditions in the winter (including ice floes to the Sea of Okhotsk). The snow in Horoka Tomamu lasts from November/December to April/May. At that time the area is only accessible by snowmobile or on skis. 


The average temperature in Shimukappu (333 metres above sea level) is 4.6 degrees celsius, with a summer high of 33.6 and a winter low of -35.8. (The altitude of Horoka Tomamu is 500 to 670 m.)


In ecosystem terms, Horoka Tomamu is hemiboreal, midway between the temperate and subarctic (boreal) zones. 


Simon and Masumi Holledge, 21 September 2010