Weather is probably a major factor when you plan your trip to Shimonoseki, and keep in mind that cheaper options are usually available when the weather isn't as good. 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 47°F. The rainiest months in Shimonoseki are July, June, August, and September, with each month seeing an average of 11 inches of rainfall.