If you're looking forward to lots of outings with your partner, check out these details about year-round temperatures in Jogakura Onsen: The hottest months are usually August and July with an average temp of 67°F, while the coldest months are January and February with an average of 28°F. The rainiest months in Jogakura Onsen are August, July, September, and October, with each month seeing an average of 8 inches of rainfall.