Weather will likely play an important role when you plan your trip to Nanseien, and keep in mind that cheaper options are usually available when the weather isn't as good. The hottest months are usually July and August with an average temp of 83°F, while the coldest months are January and February with an average of 68°F. The rainiest months in Nanseien are August, May, September, and June, with each month seeing an average of 11 inches of rainfall.