Climate - Japan

Index

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• Introduction
• Hokkaido - Abashiri, Sapporo
• Honshu - Aomori, Niigata, Tokyo, Osaka
• Kyushu - Kagoshima
• Shikoku - Takamatsu, Kochi
• Typhoons

Introduction

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The climate of Japan is cold in the north (where snow and ice dominate in winter), temperate in the central regions, and almost tropical on the small southern islands. The rains are abundant almost everywhere, and between summer and autumn the country is hit by torrential rains and typhoons.
The climate of Japan is influenced by the monsoon circulation: in winter it's affected by cold currents from the north-west, and in summer by wet and humid currents of tropical origin.

Japan is a large archipelago, consisting of more than 3,000 islands and islets, and it's very extended in latitude: Hokkaido, the northernmost of the main islands, touches the 45th parallel north (the same latitude as Montréal, Canada); Tokyo, the capital, is located on the 36th parallel (the same latitude as Malta or as Nashville, TN), while the southern part of the island of Kyushu touches the 31th parallel (the latitude of northern Egypt or of Austin, TX), and finally the small southern islands (Ogasawara, Ryukyu and Daito) reach tropical latitudes (the Yaeyama Islands, the southernmost of the Ryukyus, are located just north of the Tropic of Cancer, at the same latitude as Miami, FL).
The sea is able to temper the climate and at the same time to increase air humidity. However, the influence of the great Asian continent, of mountain ranges (which cover three quarters of the country) and ocean currents (the north-eastern sea is cooled by the cold current called Oya-Shio, while in the southern seas the warm Kuro-Shio current flows), as well as the length of the country, tend to increase the difference between the seasons and between different areas.

Two common features of the climate of Japan are the absence of a real dry season and the high summer rainfall.
Overall, the rainiest areas, where annual precipitation exceeds 2,000 millimeters (80 inches), are the central-western part of the island of Honshu (where precipitation is abundant even in winter because of the north-west monsoon), the Kii Peninsula (where the summer monsoon is actually more pronounced), also the inland and southern areas of Shikoku and the central-southern part of Kyushu (which are affected by the summer monsoon as well).
The least rainy area is the northernmost part of Hokkaido, where precipitation drops below 1,000 mm (40 in) per year, both because of the cold winter and the reduced influence of the summer monsoon.

Winter is very cold in the north (see Hokkaido and north of Honshu), with abundant snowfalls on the slopes exposed to the north-west, while it is quite mild in the centre-south, where it is rainy on the west and quite dry and sunny on the southern side (see Tokyo). In the southern islands, winter is very mild.
Summer, which begins in mid-June, is hot and muggy in much of the country, except in Hokkaido and the northern part of Honshu, where the temperatures are typically more pleasant. August is the hottest month on the main islands, while on the small southern islands there is no difference between July and August. In August, the daily average temperature is around 22 °C (71 °F) in Hokkaido, 24.5 °C (76 °F) in northern Honshu, and 28 °C (82 °F) in the area of Tokyo.
Owing to both the high humidity and the so called "urban heat island" effect, the heat is hardly bearable in Tokyo, Osaka and in the big cities of southern Honshu and Kyushu. In the hottest periods, minimum temperatures around 25/27 °C (77/81 °F) are not uncommon.
In most of Japan, summer is the rainiest season of the year.
There are two rainiest periods. The rainy season begins with the "Baiu rains" or "plum rains" (June 15-July 15), which are heavy and essential for rice cultivation, especially in the south (where June is the rainiest month of the year).
In the second part of summer, usually by August, typhoons begin to show up; they mainly affect the southern part of the country, but they may also affect Tokyo. The most intense typhoons can bring gale force winds and torrential rains, causing extensive damage.
The area of Osaka and Kyoto is relatively sheltered from typhoons because it is surrounded by mountains.
In autumn, September is still hot and humid, at least in the center and south of the country, and in Tokyo it is the rainiest month of the year. September is the rainiest month in Sapporo as well, but by this time of the year summer is already over. In contrast, the southern island of Okinawa is still in midsummer in September.

Hokkaido

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Winter is freezing on the island of Hokkaido because of cold winds from Siberia, which also cause heavy snowfalls on the slopes exposed to the north-west. In Wakkanai, on the northwest coast of Hokkaido, up to six and a half meters (260 inches) of snow fall per year. The eastern area of the island is a bit drier, but the cold sea current flowing in the Sea of Okhotsk even pushes ice floes to the north-east coast of the island; moreover, it can cause fog, especially in summer, when it meets warm air masses from the south.

Abashiri

Here are the average temperatures of Abashiri, on the northeastern coast of Hokkaido, where in February a "drift ice festival" is held. As you can see, not only is the winter cold, but the summer is not very warm.

Abashiri is one of the least rainy cities in Japan because the cold current inhibits the formation of clouds that can generate rain or snow. However, despite the fact that winter is the driest season, as high as 380 cm (150 in) of snow fall per year on average, since the temperatures are low for a long period, so it can snow from November to April.

Sapporo

In Sapporo, which hosted the 1972 Winter Olympic Games, the average temperature in January is -5 degrees Celsius (23 °F). The temperature remains below freezing (0 °C or 32 °F) from December to March, and there are 130 days with snowfall in a normal cold season. In February, the Sapporo Snow Festival is held, attracting millions of visitors to admire statues and sculptures made of ice.
Here are the average temperatures of Sapporo.

In Sapporo, 1,150 mm (45 in) of rain or snow fall per year; the (relatively) least rainy season is spring. In winter, frequent and abundant snowfalls occur. Here is the average precipitation.

The sea near Sapporo is very cold in winter (but on the north-eastern coast it's even colder), and it's still quite cool in summer, though it reaches 21 °C (70 °F) in August.



In the interior of Hokkaido, winter is even colder, and the average in January drops to -10 °C (14 °F).

Honshu

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In the northern tip of the island of Honshu, in the region called Tohoku, the winter is still freezing, with averages around -3/-2 °C (27/28 °F) in January and February. Epic snowfalls occur on the north and north-west slopes that are directly exposed to the prevailing wind.

Aomori

Here are the average temperatures of Aomori.

The yearly precipitation in Aomori is around 1,350 mm (53 inches) per year. Snowfall, which normally occurs from November to March, amounts to as much as 565 cm (223 in) per year, making it one of the snowiest plain cities in the world. The sun is rarely seen in winter; the relatively sunnier season is spring and in summer the sun does not shine very often, both because of the monsoon and because the clash between sea currents can give rise to fog.

More to the south, in the north-central part of the island (see Niigata), the average rises to 2/3 °C (36/37 °F). However, winter is still cold enough to cause frequent snowfalls on the western side, which in this season is definitely more humid than the eastern one. This is because the prevailing winds coming from Siberia, initially dry, pick up moisture from the Sea of Japan (called East Sea by the Koreans) and release it on the north-west side, while the other side is protected by the mountain ranges that cross the country like a kind of spine.

Niigata

Here are the average temperatures of Niigata, on the northwest side of Honshu.

On the western side, there is not much sun. It is seldom seen in winter, while it goes not much better during the other seasons. In Niigata, there are about 1,600 hours of sunshine per year. Precipitation in Niigata is abundant: up to 1,850 mm (72.5 in) per year. In winter, with the temperature slightly above freezing and the wind coming from the sea, it rains and snows almost every day. Here is the average precipitation.

The sea in Niigata becomes warm enough for swimming in August and September, while it is a bit cool in July and October.

While on the western side the winter is very annoying, with leaden skies, rain and snow falling almost daily, and with possible sea storms, the eastern side is protected by mountain ranges, so it experiences a fair number of sunny days (see Sendai, which is at the same latitude as Niigata but on the east coast).
The phenomenon also occurs at lower latitudes (see Kanazawa, on the west coast, and Mito, on the east coast).
Further south, the island of Honshu bends to the left, so the east coast is exposed directly to the south; here we find the main cities of Japan.
Winter in Tokyo and Osaka is the sunniest and driest season of the year; the temperatures are quite cold though bearable, with highs around 10 °C (50 °F) and lows just above freezing. On the eastern side, the winter is the sunniest season, at least as a percentage (considering that the days are shorter), while in the other seasons, more cloudy and rainy, the amount of sunshine is not high. In Tokyo, there are a bit more than 1,900 hours of sunshine per year.
Snowfalls in the capital are quite rare, and are even more rare in the conurbation that includes Osaka, Kobe and Kyoto, and in general along the south-facing coast of the Seto Inland Sea, which is protected by the mountains.

Tokyo

Here are the average temperatures of Tokyo.

In Tokyo, 1,600 mm (63 in) of rain fall per year. As we mentioned, since it lies on the south-eastern side, it is protected from the winter monsoon, so the winter here is definitely the driest season. In the other seasons it rains a lot, with a maximum in September and October. Here is the average precipitation.

During Tokyo’s winter, the sea is much warmer than in the north, becoming warm enough for swimming from July to October, and a bit cool but still acceptable in June.

In the mountainous areas, culminating in Mount Fuji, 3,778 meters (12,395 feet) high, the winter temperatures are naturally lower, and snow is abundant, especially on the western slopes. On the island of Honshu, there are famous ski resorts such as Morioka, in the far north, and Nagano, northwest of Tokyo, which hosted the 1998 Winter Olympics.
Here, for example, are the average temperatures in Karuizawa, a resort town located at 1,000 meters (3,300 ft) of altitude in the Nagano prefecture, northwest of Tokyo, where the capital's inhabitants flock during summer to escape the heat.

In some mountainous areas, such as in Mount Zao, a curious phenomenon occurs, known as "snow monsters", whereby the moisture carried by the wind is deposited as ice on the trees.

Kyushu

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On the island of Kyushu, the winter climate is relatively mild, but it's quite rainy. In January, the average goes from 6/7 °C (43/45 °F) on the north coast (see Kitakyushu, Fukuoka) to 9 °C (48 °F) on the south coast.
The west coast is particularly rainy (see Nagasaki, Kagoshima), especially in June: in some areas, even at sea level, rainfall exceeds 500 mm (20 in) per month!

Kagoshima

Here is the average precipitation in Kagoshima.

Here are the average temperatures in Kagoshima.

The sea in the southern part of Kyushu is never cold, but it becomes cool in winter, in fact the water temperature drops to 19 °C (66 °F) in February.

Shikoku

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In Shikoku, the smallest of the main islands of Japan, the climate is temperate, quite similar to that of the south side of Honshu: the winters are quite cold, and the summers are hot, muggy and rainy. The north coast is a little colder in winter than the south coast, and definitely less rainy.

Takamatsu

Here are the average temperatures in Takamatsu, on the north coast.

As for the rains, there is a clear difference between the two sides. The north side has a dry winter, and the annual rainfall is not very high, in fact it's around 1,150 mm (45 in) per year in Takamatsu, 1,200 mm (47 in) in Maragume, and 1,400 mm (55 in) in Matsuyama.
Here is the average rainfall in Takamatsu.

Kochi

In Kochi, on the southern coast, the winter temperatures are slightly higher, and the January average is 7 °C (44 °F).

The south side is decidedly more rainy: in Kochi, 2,550 mm (100 in) of rain fall per year, and the rains are very abundant from April to September. However, here the winter is a relatively dry season too.

The sea in Kochi is pleasantly warm for swimming from July to September, while it becomes quite cold in winter.

In the mountainous area that divides the two sides of Shikoku, the temperature decreases, even though at the same altitude it is not as cold as in the center-north of Honshu. Here are the average temperatures of Mount Tsurugi, 1,955 meters (6,413 feet) high.

To the south of the main islands we find some archipelagos made up of smaller islands. The southern islands of Japan have generally a rainy climate, and progressively milder as you go south.

Typhoons

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As mentioned earlier, Japan can be hit by typhoons, the tropical cyclones of the western Pacific.
Typically, typhoons occur from June to October. Occasionally they have also occurred before and after this period (so, from late April to late May, and from early November to early December). However, they are more frequent from August to early October; the strongest ones have occurred in September. As regards to wind and waves, the most affected areas are the southern islands (Ryukyu, Daito, Ogasawara), which are hit by typhoons during their highest intensities. However, the main islands, especially Kyushu, Shikoku and the south side of Honshu, can receive heavy rains, which increase on the mountain slopes and can cause floods and landslides, while there may be abnormal waves along the coasts. In northern Honshu and in Hokkaido, typhoons arrive generally weakened, but they can still bring abundant rains, and sometimes even strong winds.



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