If you’re hoping to get lost in the rain on your romantic getaway, check out these details about year-round temperatures in Kirishima: The hottest months are usually August and July with an average temp of 75°F, while the coldest months are January and February with an average of 46°F. The rainiest months in Kirishima are June, July, May, and September, with each month seeing an average of 16 inches of rainfall.