Planning for the weather is a good way to make your trip to Kumamoto relaxing and enjoyable, especially when you’re splurging. The hottest months are usually August and July, with an average temperature of 25°C, while the coldest months are January and February, with an average of 8°C. The rainiest months in Kumamoto are June, July, August and May, with each month seeing an average of 331 mm of rainfall.