Overall the Japanese climate is temperate, with four clearly defined seasons. But there's considerable variation in temperature from north to south, since the country extends over 25 degrees of latitude. In Hokkaido, the big island of the north, the average temperature during the coldest month of the winter is below -6 degrees Celsius (21 degrees Fahrenheit). The inland basin areas, like those surrounding the cities of Obihiro and Asahikawa, are especially cold; it is common for temperatures to dip below -30 degrees Celsius (-22 degrees Fahrenheit). The lowest temperature ever observed in Japan was -41 degrees Celsius (-42 degrees Fahrenheit), recorded in Asahikawa in January, 1902.
The southernmost part of Japan, the islands including Okinawa, have a sub-tropical climate with long, hot, and humid summers. In Naha, the capital of Okinawa Prefecture, the year-round average temperature is 22.6 degrees Celsius (73 degrees Fahrenheit), and even during the winter the lowest monthly average is 13.6 degrees Celsius (56 degrees Fahrenheit). Because the islands of Okinawa are relatively small, ocean breezes keep them from getting too hot in the summer. The highest monthly average temperature is 32.2 degrees Celsius (90 degrees Fahrenheit). The hottest summer weather is to be found around Tokyo and in some other parts of Honshu, Japan's main island, where the temperature can reach almost 40 degrees Celsius (104 degrees Fahrenheit). In July 2010, a high of 39.4 degrees Celsius was recorded in Tajimi, Gifu Prefecture.