Planning for the weather is an important factor for making your trip to Okushiri a success, especially when you're splurging. The hottest months are usually August and September with an average temp of 68°F, while the coldest months are January and February with an average of 35°F. The snowiest months in Okushiri are January, February, March, and December, with each month seeing an average of 30 inches of snowfall.