If you’re looking forward to lots of outings with your partner, check out these details about year-round temperatures in Iizuka: 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 46°F. The rainiest months in Iizuka are July, June, August, and September, with each month seeing an average of 9 inches of rainfall.