If you’re looking forward to lots of outings with your partner, take a look at these details about year-round temperatures in Nishinomiya: The hottest months are usually August and July, with an average temperature of 24°C, while the coldest months are January and February, with an average of 6°C. The rainiest months in Nishinomiya are July, September, June and August, with each month seeing an average of 267 mm of rainfall.