Planning for the weather is a good way to make your trip to Akasaki Onsen relaxing and enjoyable, especially when you’re splurging. The hottest months are usually August and July with an average temp of 74°F, while the coldest months are January and February with an average of 41°F. The rainiest months in Akasaki Onsen are July, September, August, and December, with each month seeing an average of 10 inches of rainfall.