If you’re looking forward to lots of outings with your partner, check out these details about year-round temperatures in Kisarazu: The hottest months are usually August and July with an average temp of 76°F, while the coldest months are January and February with an average of 48°F. The rainiest months in Kisarazu are October, September, June, and July, with each month seeing an average of 9 inches of rainfall.