April, some snow is still there in the shade and we occasionally have snowy weather. So we need winter equipments to stay here. Buds of plant are still tight, winter landscape is still here.
In the middle of April, willow and amur adonis finally bloom. At the end of April, it is full-blown season of shooting buds and the season of child-bearing for monkeys.
Flog, lizard and snake come out from their hibernation. Migrant birds, such as Blue-and-white flycatcher, Siberian blue robin and Narcissus flycatcher reach here.
May, the green grows deeper. Terpnosia nigricosta buzzes in the forest. June, it is the child-birth season of the Japanese serow followed monkeys’. If you are lucky, you may meet baby serows.
Bloom of Tea-of -heaven tells us the beginning of summer.
You should bring a light jacket until the end of rainy season.
Full-blown summer starts after the end of rainy season. Buzzing of cicadas changes from Ezo-haruzemi (Terpnosia nigricosta) to Abra-zemi (Graptopsaltria nigrofuscata) and Minmin-zemi (Oncotympana maculaticollis).
Birds and animals, including monkeys, stay in the shade to avoid the burning sun when the temperatures increase.
You can see dragonfly and butterfly, especially Miyamakarasu-ageha (Papilio maackii).
We wouldn’t recommend wearing beach sandal or slipper even in summer season. Because there are plants with aculeus such as stinging nettle and eglantine, and also poisonous snake such as pit viper and tiger keelback. You have to be careful about mosquito, bee and gadfly.
We rarely have over 30 degrees centigrade here in Jigokudani during summer season because of the altitude, it’s over 800m. Summer in Jigokudani is short. There is a nip of fall in the air in the mid-August.
September, the lingering summer heat is still there though the harvest season starts in the forest. There are plenty of nuts and fruits such as walnut, grape, beechnut and chestnut. Buzzing of cicada trails off when the autumn flowers (bush clover, jewelweed, water pepper) bloom.
Summer birds leave and we see many red dragonflies in this valley. Not only monkeys but other animals move actively for preparation of winter season. Squirrels run on the nature trail carrying nuts to their den.
The season of autumn leaves come to the valley beyond the mid- October.
In November, temperatures go down to below zero and we sometimes have frost. Then we have first snow and trees in the forest shed its leaves to wait for winter.
In the mid-December, we usually have heavy snow. Accentors come from high mountains to Jigokudani to overwinter when snow covers the mountains.
In this season we can observe the Japanese serow easily because they (monkeys also) are on sunshiny southern slopes for long time.
The temperatures are always below zero, the lowest is minus 10digrees centigrade.
The valley of Jigokudani is very deep so the sunshine does not reach to the bottom. That’s why monkeys take the hot spring to ward off the cold.
Even warm winter has been continuing recent years, it is normal that snow accumulates 40cm-50cm in one night. The accumulated snow will be over 100cm during the coldest period between January and February. If you visit Jigoku-dani this season, you should have adequate equipments for cold protection.