Planning for the weather is an important factor for making your trip to Sannai a success, especially when you're splurging. The hottest months are usually August and July, with an average temperature of 18°C, while the coldest months are January and February, with an average of -2°C. The snowiest months in Sannai are January, February, March and December, with each month seeing an average of 77 cm of snowfall.