If you’re hoping to get lost in the rain on your romantic getaway, check out these details about year-round temperatures in Nirasaki: The hottest months are usually August and July with an average temp of 70°F, while the coldest months are January and February with an average of 35°F. The rainiest months in Nirasaki are September, July, October, and June, with each month seeing an average of 11 inches of rainfall.