Climate in Japan

The climate of Japan is temperate with cold winters in the north, where snow and ice dominate in winter, subtropical 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).
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, and the 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.

In addition, the mountain ranges, which occupy the interior areas of the islands and cover three quarters of the country's surface, create differences between the slopes. The highest peak in the country is Mount Fuji, 3,778 meters (12,395 feet) high, located on the island of Honshu, southwest of Tokyo.

In these mountains, there are winter sports resorts, such as Morioka, in the far north of Honshu, and Nagano, northwest of Tokyo, which hosted the 1998 Winter Olympics. There is usually snow for skiing from December to March, but also in April in the north and in the higher mountains.

Two common features of the climate of Japan are the absence of a real dry season and the high summer rainfall.

In the following map, we can see the climate zones in Japan (excluding the southernmost islands).



At sea level, precipitation is moderate on the northern island of Hokkaido, where it typically ranges from 850 to 1,150 millimetres (33.5 to 45.5 inches) per year, both because of the cold winter and the reduced influence of the summer monsoon. For the rest, rainfall is generally abundant in central and southern Japan, where it typically ranges from 1,300 to 2,000 mm (51 to 78 in) per year. In Tokyo, 1,600 mm (63 in) of rain fall per year.
The rainiest areas, where annual precipitation reaches 2,500 millimeters (98 inches), are, in addition to the central-western portion of the island of Honshu (where precipitation is abundant even in winter because of the north-west monsoon, see Kanazawa), the southern coasts of Honshu, Kyushu and Shikoku, facing the Pacific Ocean, where the effects of the summer monsoon, as well as the rains brought by typhoons, are particularly felt.
However, there are also small areas where 4 meters (157 in) of rain per year are reached (see Owase, on the Kii Peninsula, Honshu) and even 4 and a half meters (177 inches, see the small island of Yakushima).

The climate in detail

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• The seasons
• Typhoons
• When to go
• What to pack
• Climate data

The seasons

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Winter is very cold in the north, with an average temperature below freezing in Hokkaido and northern Honshu, and with abundant snowfalls on the slopes exposed to the north-west.
Instead, the winter is quite mild in the centre-south, and it is rainy, and sometimes snowy, on the north-western side, and quite dry and sunny on the south-eastern side (see Tokyo, Osaka). In the latter area, snowfall is rare.
On the small southern islands (see Okinawa), there is a very mild, spring-like winter.
The average temperature in January ranges from -10 °C (14 °F) in the coldest areas of Hokkaido, to 6 °C (43 °F) in Tokyo, to more than 15 °C (59 °F) on the small southern islands.



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 average temperature in Hokkaido ranges from 17 °C (62.5 °F) in the coolest area, the northeastern coast, to 22 °C (71.5 °F) in Sapporo. In Honshu, the average ranges from 24 °C (75 °F) in the north to 28 °C (82 °F) in the Tokyo area, to almost 30 °C (86 °F) in Osaka.
Owing to both the high humidity and the so called "urban heat island" effect, the heat is hardly bearable in Tokyo and Osaka, and in the other large cities of central and southern Japan. 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", which are heavy and essential for rice cultivation, and affect Okinawa and the small southern islands in May and June, and the south-west of the country (Kyushu, Shikoku and southern Honshu) approximately from early June to mid-July. For this reason, June is the rainiest month of the year in southern Japan.

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.

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. Especially in the southern islands, 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.

When to go

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The best time to visit Japan is spring, from mid-April to mid-May in Tokyo and in the main cities of south-central, a month later in Hokkaido.
Or you can go a couple of weeks earlier, although the weather is cooler, to admire the cherry blossoming (hanami). In Tokyo and Osaka, the full bloom occurs around March 30th, in Sendai around April 15th, in Sapporo around May 5th, in Okinawa even around February 1st.
The flowering tends to last longer in the south than in the north (about two weeks in the south, one week in Hokkaido, and even one month in Okinawa), and the date can vary by a few days or one week, before or after, depending on the year.



In autumn, the forests and the trees around the temples take on beautiful colors: the period in which you can go in search of trees turning red (momijigari), especially maples, varies depending on area: in Hokkaido it goes from late September to late October (but already in mid-September in inland mountainous areas), in northern Honshu from October to early November, in Nikko and in the area of lake Chuzenji from early October to mid-November, in central and southern Japan and in Kyoto from mid-November to early December.
If you want to go in autumn, you can choose the period mid-October to mid-November, by which time the risk of typhoons is reduced, as well as the heat in the south, or you can choose the period of the fall foliage. In October, the temperatures are already cool in Sapporo, while they are pleasant in the rest of Japan, air humidity has decreased and the rains are less abundant.

If you prefer to go in winter, for example at New Year, you can choose the most sheltered and sunny area of Honshu (Tokyo, Osaka, Kyoto), or the southernmost part of the other main islands (Kagoshima, Kochi) and the tropical area (Okinawa, Daito, Ogasawara).

If you want to visit the main cities in summer, August is partly preferable to July, having more sunshine and less rainfall, but it is also true that it is hotter and there's a greater risk of typhoons.

Being rainy and not very sunny in summer, Japan is not the best country for swimming and sun bathing. Anyway, as we said before, in Hokkaido the sea is a bit cool even in this season, while it's quite warm, with a temperature equal to or higher than 23 °C (73 °F), for most of the year in Okinawa, from July to October in Tokyo and Yokohama, and in August and September in Niigata.
Since there is a pause between the two rainy periods (May-June and August-September), in Okinawa the best month for a beach holiday is July, though afternoon thunderstorms are still possible, in addition to the passage of tropical storms and typhoons over the island.

What to pack

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In winter: in Hokkaido and northern Honshu, up to Niigata and Fukushima bring very warm clothes such as synthetic thermal long underwear, especially for Hokkaido, a fleece, a down jacket, gloves, a scarf, a hat, and a raincoat.
In the area of Tokyo, Kyoto and Osaka, warm clothes, such as a sweater, a jacket, a hat, and possibly a raincoat or umbrella.
In Okinawa and the small southern islands, spring/autumn clothes, a sweatshirt or sweater, a jacket, a raincoat or umbrella.

In summer: in northern Hokkaido, spring/autumn clothes (light for the day), a sweater and a raincoat. In Sapporo and northern Honshu, light clothing, a sweatshirt and a light jacket, a raincoat or umbrella.
Throughout south-central Japan and the small islands, including Okinawa and Tokyo, light, tropics-friendly clothing, a scarf for the breeze, a light sweatshirt for the evening and air conditioned places, a light raincoat or umbrella. For the mountainous areas, warmer clothes depending on altitude, spring/autumn clothes at about 2,000 meters (6,500 feet) in Honshu.
When going to the reef, you can bring snorkeling equipment, including water shoes or rubber-soled shoes.
It is customary to remove shoes before entering homes and temples, so it can be useful to wear shoes without laces, or that are at least easy to take off.

Climate data - Japan

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See also the temperatures month by month