Weather will likely play an important role when you plan your trip to Kamisuwa Onsen, but bear 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 temperature of 19°C, while the coldest months are January and February, with an average of -1°C. The rainiest months in Kamisuwa Onsen are July, October, September and June, with each month seeing an average of 203 mm of rainfall.