Japan's Climates
 
 
 
 

    Japan has a range of climates typical of middle latitudes and similar to that of the east coast of most of North America.

    Hokkaido and the interior of northeastern Honshu have a humid continental climate, characterized by short, cool summers and long, cold, and often snowy winters. Summers become warmer and longer, and winters become shorter and milder toward the south, where subtropical conditions prevail. Demonstrating this latitudinal change in climate, Sapporo, on Hokkaido, has a January mean temperature of - 6 degrees C (21 degrees F) and a July temperature of only 19 degrees C (67 degrees F)
    Tokyo averages 3 degrees C (38 degrees F) in January and 26 degrees C (76 degrees F) in July; and Nagasaki, in the southwest, averages 6 degrees C (42 degrees F) in January and 26 degrees C (79 degrees F) in July.

The wind and rainfall patterns are primarily influenced by the monsoon system typical of East Asia. In winter, cold winds blow outward from the Asian continent, reaching Japan from the northwest and the Sea of Japan; in summer, warm, moist winds are drawn toward the Asian interior, blowing across Japan from the Pacific Ocean. As a result, coasts facing the Pacific receive the most precipitation from mid-June to mid-July, while the northeast coast receives heavy winter precipitation from the northwest monsoon, much of it in the form of snow. Average annual precipitation for most of Japan is 1,270 mm (50 in), with some mountain areas receiving up to 2,540 mm (100 in). The Inland Sea area is somewhat drier because it is protected by surrounding mountain chains; it receives only 1,016 mm (40 in) to 1,524 mm (60 in).
 

 
 
 
 
Japan's climate is also strongly influenced by two ocean currents and occasional storms and typhoons. The Japan Current (or Kuro Shio), a warm ocean current, flows northward through the islands; its warm waters moderate winter temperatures along the entire southern coast and, to a lesser extent, the southern coastal areas facing the Sea of Japan. By contrast, the cold Okhotsk Current originates in polar waters and flows southward along Hokkaido, contributing to the harsh climate of that island. Typhoons occur from late August to early October; they are accompanied by often devastating high winds and heavy rains, but the storms are also valued because they bring moisture during an otherwise dry season.