Planning for the weather is a good way to make your trip to Sumita relaxing and enjoyable, especially when you're splurging. The hottest months are usually August and July, with an average temperature of 21°C, while the coldest months are February and January, with an average of 2°C. The rainiest months in Sumita are September, October, August and July, with each month seeing an average of 188 mm of rainfall.