If you’re looking forward to lots of outings with your partner, check out these details about year-round temperatures in Moriguchi: The hottest months are usually August and July with an average temp of 77°F, while the coldest months are January and February with an average of 43°F. The rainiest months in Moriguchi are July, June, September, and October, with each month seeing an average of 8 inches of rainfall.