Planning for the weather is a good way to make your trip to Atami 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 45°F. The rainiest months in Atami are June, September, July, and October, with each month seeing an average of 12 inches of rainfall.