The climate of Japan is characterized by four seasons. the spring season are from March to May, Summer season are from June to August, Autumn from September to November and Winter from December to February. The deference between summer temperature and winter temperatures is more than 30 degree Celsius. Summer season, with high temperature and high humidity, maybe uncomfortable for people who are use to dry climate. In the spring and autumn almost all part of Japan enjoy the comfortable temperature, but the weather is very changeable.
All area except Hokkaido have a rainy season in beginning of summer,which is from early June to mid-July. From end of summer to beginning of autumn, generated typhoon in th e western part of North Pacific Ocean hit the country, sometime causing big damage.
Majority of Japanese would say that the best season for traveling are spring and autumn, especially early May when tree are green, and between a September to end of November when leaves change colors. The weather is pleasant to enjoy traveling.
But winter is our dry season during end of November to end of January, You can see the Mt Fuji very clearly and mountain ranges are covered full of the snow.