Weather is probably a major factor when you plan your trip to Miyakonojo, 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 75°F, while the coldest months are January and February with an average of 46°F. The rainiest months in Miyakonojo are June, July, September, and May, with each month seeing an average of 15 inches of rainfall.