Weather in Japan
Author: Edutraveller
Date written: 04/19/2003 03:51:01 PM
Last edited: 2003/05/25 16:53:08
Keywords: Japan travel guide, Japanese weather, Weather in Japan, Japanese seasons, Summer, Winter, Spring, Autumn, Fall
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Weather and climate
Japan is not a particularly large country but it is very long, covering approximately 20 degrees of latitude from the far north to the southernmost islands. The resulting range of climates is from the cool temperate in Hokkaido and northern Honshu, to subtropical in the southern Ryukyu islands and Ogasawara (Bonin) islands. Its mountainous terrain also lends to the variation, with higher central areas experiencing significantly different temperatures to lower coastal ones. The central mountain range, the Japan Alps, also creates a significant difference in rainfall between east and west. This pattern of north-south, east-west, and high-low contrasts underlays the Japanese climate.
Seasons
While the weather within the Japanese archipelago is far from the same everywhere, it is possible to discover some rough patterns. The year in Japan is divided into four fairly clearly defined seasons. Summer is generally hot and humid, and lasts from June through to August. Winter is cold and dryer, and stretches from December to February. The intervening Spring and Autumn months are the most pleasant in the year, particularly April to May (March can still be very cold at times) and October and November (September is still sometimes too hot and sweaty for comfort).
The rainy season (tsuuyuu) lasts from June to early July, but arrives early or late sometimes. Typhoons formed in the Pacific move towards Okinawa, then gradually work their way up the archipelago, with typhoons that come later in the year hitting the Japanese islands furhter and further to the north. When typhoons come, they bring high winds and torrential rains, but generally also clean, cool air, making the aftermath quite pleasant (if you didn't get soaked, of course). Although tsuyuu is not the best time to travel, typhoon warnings are very efficient so you can plan your activities around and between them and there is no reason to avoid holidaying or traveling in Japan at this time.
If you intend to take part in rafting or other river activities, these are usually suspended during the rainy season. If camping near rivers, take extreme care during this season as rivers regularly burst their banks and may rise several meters in a few minutes. If you are careful, camp only on high ground and pay attention to weather forecasts, you have nothing to fear.
Regional variations
The main actors affecting Japanese weather patterns are the warm mass of the Pacific Ocean, particularly the warm Kuroshio current; the Japan Sea; and the cold airs of Siberia. These three combine to produce a unique weather system that is both monsoonal and wet as a tropical climate yet temperate in its range. The Japanese archipelago is by far the wettest of any temperate climate in the world.
As mentioned above, the north of Japan is colder than the south, and has heavy snowfall, but suffers less rain. The warm Kuroshio current brings with it warm, damp air, and also the typhoons and heavy rain of summer. This warm water passes along both sides of Japan, and on the continental side meets with cold, Siberian air in winter, bringing heavy snowfall to the western side of Honshu and all of Hokkaido. In summer, there is not noticeably more rain on either side due to different air patterns.
Average temperatures for six major cities are shown on the chart above. As you can see, the trend in temperature change is uniform across Japan, but with a higher average in the south and lower in the north (the annual average temperature in Sapporo is 8.5°C, Okinawa is 22.7°C, while the middle part of Japan is around 16°C. Basically, the north of Japan and also the Japan Sea coast are colder in winter with more snow, while the Pacific side and the south of Japan are warmer. Okinawa is of course the warmest of all.
The picture regarding rainfall is a little less clear. Most rainfall in Japan occurs in the typhoon season between June and September. However, there is also significant snowfall in parts of Japan during the winter. Naha (Okinawa) and Sapporo (Hokkaido) show the trend that typhoons tend to the north as the year progresses: the typhoon rainfall peak occurs later in Hokkaido than in Okinawa. Total rainfall is highest in the south and coastal areas of central Japan, and much lower in other areas of central and northern Japan. As mentioned above, however, most of this rainfall is concentrated in the typhoon season, and Japanese weather forecasts are fairly accurate.
Average sunshine hours differ little over the country, except for a slight trend to more sunshine in the south due to latitude (although Okinawa shows its higher rainfall with consequently less sunshine).
Travel and education
If you are thinking of travelling in Japan, then you can really come any time. It makes little difference if you are studying, but if you intend to take part in outdoor activities (particularly camping and hiking around rivers, or white-water rafting, etc.) then you should make sure that you avoid the rainy season or pay very close attention to weather forecasts and have contingency plans in case you cannot do what you intended to. There are always plenty of things to do in Japan, at any time of year, so you will always be able to enjoy a holiday, whatever the time of year.
Sources
UK Met Office (British Government
Meteorological Office) Japan
page.
Links
Japan Weather Association has satellite pictures of Japan and Asia, updated hourly, so you can see cloud conditions. Their English site is rather limited, but does include regional weekly forecasts.
If you can read japanese, perhaps the best site for weather information (including streaming video of weather forecasts in Japanese) is tenki.or.jp. You can also get information on typhoons, tsunami and active volcanoes. But don't worry, 123 million people manage to live with the pretty much without incident.
TBS television also offers free information and forecasts.
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