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The Japanese Climate
[2016.06.25] Read in: FRANÇAIS | ESPAÑOL | العربية | Русский |

From subarctic Hokkaidō to subtropical Okinawa, Japan’s climate varies greatly by region.

Snow in the North, Blossoms in the South

When Hokkaidō in northern Japan is still buried in snow in January, cherry blossoms come into full bloom in the southern islands of Okinawa. Stretching like a bow off the east of the Eurasian continent, the Japanese archipelago shows great climatic variation within its approximately 3,000 kilometers of length from northeast to southwest. It consists of more than 6,800 islands—the four largest are Hokkaidō, Honshū, Shikoku, and Kyūshū—and has around 30,000 kilometers of coastline, which is longer than that for the United States. Some 75% of the country is mountainous, and the Japanese Alps and other ranges occupy large swaths of the main island of Honshū. The Japanese capital Tokyo has a latitude of around 35°N—similar to Los Angeles and Athens—and a longitude of around 139°E, which is almost the same as Adelaide in Australia.

As the map below shows, Japan is divided into various climate zones from subarctic Hokkaidō to subtropical Okinawa. In winter, winds from Siberia pick up moisture as they cross the water, bringing rain and snow to the Japan Sea side of the country. Buffered by the central mountain ranges, the Pacific side of Japan enjoys fine weather in winter. By contrast, in summer the Pacific side of the country is rainier, due in part to typhoons, while the Japan Sea side has mostly sunny days.

1 Japan Sea 1a Okhotsk Average temperature below 0°C in winter. Low annual rainfall.
1b Tōhoku; Hokkaidō Heavy rainfall in September and winter. Average temperature below 0°C in January and February
1c Hokuriku; San’in Average monthly temperature does not fall below 0°C. Heavy snow in winter.
2 2 Kyūshū Heavy rainfall in June and July.
3 3 Nankai Heavy rainfall all year round, particularly around June and September.
4 4 Setouchi Warm with low rainfall all year round
5 East Japan 5a East Hokkaidō Severely cold in winter. Low rainfall, except around September when it is high.
5b Sanriku; Jōban Lower temperatures and less snow compared with the Japan Sea side at this latitude.
5c Tōkai, Kantō Heavy rain around June and September to October. Fine weather in winter.
5d Chūō kōgen Great seasonal variation in temperature. Severely cold in winter with little accumulation of snow.
6 6a Nansei shotō Warm with little seasonal variation in temperature. Low rainfall.
6b Chichijima Warm with little seasonal variation in temperature. Heavy rainfall in May and November.

List created by Nippon.com editorial staff based on textbook data produced by Ninomiya Shoten.

The Coming of Spring

The first strong south wind of the year heralds the coming of spring to people on the Pacific side of Japan. It is called the haru ichiban—literally “spring first”—and blows in between February and mid-March. Cherry blossom season with its hanami picnics under the trees starts in Okinawa in January. The movement of the sakura zensen or “cherry blossom front” up the country is followed by media reports until it reaches Hokkaidō in May.

As well as the standard four seasons, most of Japan has a rainy season known as tsuyu, lasting around six weeks from late spring or early summer, depending on the area. Hokkaidō is the only part of the country that avoids this sticky, showery time of year.

Summers have been getting hotter with temperatures more frequently rising above 30°C and even sometimes topping 40°C. The highest ever temperature recorded in Japan was 41°C in Kōchi Prefecture, Shikoku, in August 2013. Since 2008, “guerrilla rainstorms” have also become an increasingly regular phenomenon. In these sudden localized downpours, more than 50 millimeters of rain falls per hour.

Getting Through Summer

Uniforms at public organizations, corporations, and schools change to match the passing of the seasons in a custom known as koromogae—literally “clothes change.” In most cases, summer uniforms come in on June 1 to be replaced again by winter outfits on October 1. In Japanese homes, which often have limited storage space, summer clothes may come out of boxes to be hung in wardrobes. At the same time, winter coats and clothes are put away in cases, together with dehumidifying agents to prevent mold. The custom of koromogae is said to date back to the Heian period (794–1185).

Summer (left) and winter (right) school uniforms.

Companies without a uniform are recommended by the Ministry of the Environment to follow the Cool Biz dress code from May 1 to October 31. Under these guidelines, employees do not have to wear jackets or neckties. Among the many approaches to Japan’s sweltering summer, the use of air conditioning and electric fans continues to be popular. Handheld fans, bamboo blinds, anti-UV curtains, and wearable ice-pack “neck coolers” enjoy a bump in sales at this time of year, while some people cool streets and gardens with water in a tradition known as uchimizu. There is also increased interest in the environmentally friendly practice of growing climbing plants like gōya (bitter melon) and morning glory on the outside of buildings to create “green curtains” that limit the amount of heat entering through windows and reduce the need for cooling.

A “green curtain” blocks out the sun’s rays.

Tape for sealing out drafts.

Toward the end of the year, as the cold nights set in, it is time to bring heaters and kotatsu tables out again. Householders head to ¥100 shops to stock up on tape for sealing the edges of windows and keeping drafts out. Aluminum sheets under carpet are another way to keep the cold at bay. Insulation and double-glazed windows are still not common in most of Japan.

Changing Climate

In Japan, April is the start of the new school year and by extension the time when new hires begin working at companies. Entrance ceremonies are held in both educational and corporate settings and commemorative class photographs are often taken against a cherry blossom backdrop. Summer vacation at schools usually lasts from late July to late August. In Hokkaidō and other areas that experience heavy snow, however, the summer vacation is a little shorter with more time taken off in winter instead.

New first-graders and cherry blossoms.

The passing of the seasons is a common theme in the Japanese arts, exerting an influence on poetry, painting, the tea ceremony, ikebana flower arrangement, cuisine, and more. It is no exaggeration to say that Japan’s traditional culture would be nothing without words to describe the seasons.

Urbanization and the reduction in green space have transformed the country’s landscape. At the same time, it has become more difficult to predict when plum or cherry blossoms will open due to a changing climate. Event organizers worry that irregular weather patterns are increasingly disrupting these essentially Japanese observances.

▼Further reading
Hot and Getting Hotter Japan’s 72 Microseasons “Guerrilla Rainstorms” Assault Tokyo

(Banner photo: A hikan-zakura blooms in January in Okinawa, while snow covers the Yōteizan mountain in Hokkaidō.)

  • [2016.06.25]
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