Weather will likely play an important role when you plan your trip to Jiseiji Onsen, and keep in mind that cheaper options are usually available when the weather isn't as good. The hottest months are usually August and July with an average temp of 76°F, while the coldest months are January and February with an average of 45°F. The rainiest months in Jiseiji Onsen are July, June, August, and September, with each month seeing an average of 11 inches of rainfall.