Planning for the weather is a good way to make your trip to Otaru relaxing and enjoyable, especially when you’re splurging. The hottest months are usually August and July with an average temp of 64°F, while the coldest months are February and January with an average of 23°F. The snowiest months in Otaru are January, February, March, and December, with each month seeing an average of 30 inches of snowfall.