Planning for the weather is an important factor for making your trip to Kotaniishi a success, especially when you're splurging. The hottest months are usually August and July, with an average temperature of 19°C, while the coldest months are January and February, with an average of 0°C. The snowiest months in Kotaniishi are January, February, March and December, with each month seeing an average of 77 cm of snowfall.