Japan's most comfortable seasons are spring and fall. In spring the country is warm, with occasional showers, and flowers grace landscapes in both rural and urban areas. The first harbingers of spring are plum blossoms in early March; sakura (cherry blossoms) follow, beginning in Kyushu and usually arriving in Tokyo by mid-April.
Summer brings the rainy season, with particularly heavy rains and stifling humidity in June and July. Avoid July and August, unless you're visiting Hokkaido, where temperatures are more bearable. Fall relieves with clear blue skies and glorious foliage. A few surprise typhoons may occur in early fall, but the storms are usually as quick to leave.
Winter is gray and chilly, with little snow in most areas along the Pacific Ocean side of the country, where temperatures rarely fall below freezing. Hokkaido and the Japan Sea side of the country (facing Korea and Russia) are a different story, with heavy snowfalls in the winter months.
To avoid crowds, be aware of times when most Japanese are vacationing. Usually, Japanese vacation on the same holiday dates. As a result, airports, planes, trains, and hotels are booked far in advance. Many businesses, shops, and restaurants are closed during these holidays. Holiday periods include the few days before and after New Year's; Golden Week, which follows Showa Day (April 29); and mid-August at the time of the Obon festivals, when many Japanese return to their hometowns.