Planning for the weather is a good way to make your trip to Niigata relaxing and enjoyable, especially when you're splurging. The hottest months are usually August and July, with an average temperature of 23°C, while the coldest months are February and January, with an average of 5°C. The rainiest months in Niigata are July, December, January and August, with each month seeing an average of 215 mm of rainfall.