If you’re looking forward to lots of outings with your partner, check out these details about year-round temperatures in Nichinan: The hottest months are usually August and July with an average temp of 78°F, while the coldest months are January and February with an average of 53°F. The rainiest months in Nichinan are June, July, September, and August, with each month seeing an average of 16 inches of rainfall.