Weather will likely play an important role when you plan your trip to Rishiri, but bear in mind that cheaper options are usually available when the weather isn't as good. The hottest months are usually August and September, with an average temperature of 17°C, while the coldest months are January and February, with an average of -2°C. The snowiest months in Rishiri are January, February, March and December, with each month seeing an average of 77 cm of snowfall.