Planning for the weather is a good way to make your trip to Kannawa Onsen relaxing and enjoyable, especially when you’re splurging. The hottest months are usually August and July, with an average temperature of 23°C, while the coldest months are January and February, with an average of 6°C. The rainiest months in Kannawa Onsen are June, July, September and August, with each month seeing an average of 275 mm of rainfall.