Weather is probably a major factor when you plan your trip to Yashima, but bear 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 temperature of 20°C, while the coldest months are February and January, with an average of -1°C. The rainiest months in Yashima are July, August, December and September, with each month seeing an average of 205 mm of rainfall.