There's nothing like an all-inclusive holiday in Kamimoku Onsen to revive you, especially when you know what kind of weather to expect. Here's some information to help you choose when to book: The hottest months are usually August and July, with an average temperature of 20°C, while the coldest months are January and February, with an average of 0°C. January and December are the driest months, while July and September are the rainiest months.