In Japan: 
The Japanese summer begins in June with a three to four week rainy season. This is an important time for farmers to plant rice. It becomes seriously hot and humid from July onward and many Japanese enjoy bathing in the sea and relaxing at cool resorts in mountainous areas. Summer is when many interesting festivals and other events are held all over the country

For the Travelers:

On the down side, the sticky summer months can turn even the briefest excursion out of the air conditioning into a soup bath; on the plus side, major tourist attractions will generally be quieter at these times of the year.

Clothing: light clothes (cardigans and other similar kinds are handy, since indoors are mostly air-conditioned.)

 Japan's Summer Festival