The combination of Japan’s mountainous territory and the length of the archipelago (covering about 20° of latitude) makes for a complex climate. Most of the country is located in the northern temperate zone, which yields four distinct seasons. In addition, there are significant climatic differences between Hokkaidō in the north, which has short summers and lengthy winters with heavy snowfalls, and the southern islands, such as Okinawa in Nansei-shotō (Southwest Archipelago), which enjoy a subtropical climate.
In the winter months (December to February), cold, dry air-masses from Siberia move down over Japan, where they meet warmer, moister air-masses from the Pacific. The resulting precipitation causes huge snowfalls on the side of the country that faces the Sea of Japan. The Pacific Ocean side of Japan receives less snow but can still be quite cold, while the big cities of Honshū like Tokyo, Osaka, Nagoya and Kyoto have winters with highs in the single digits or even low teens and lows a few degrees above zero (Celsius). The odd January or February day will be colder, but these cold snaps usually don’t last.
The summer months (June to August) are dominated by warm, moist air currents from the Pacific, and produce high temperatures and humidity throughout most of Japan (with the blissful exception of Hokkaidō). In the early part of summer, usually mid-May to June, there is a rainy season lasting a few weeks that starts in the south and gradually works its way northward. Although it can be inconvenient, this rainy season is not usually a significant barrier to travel. August, September and October is typhoon season, which can make travel in Okinawa, the Izu-shotō and Ogasawara-shotō difficult.
In contrast to the extremes of summer and winter, spring (March to May) and autumn (September to November) in Japan are comparatively mild. Rainfall is relatively low and the days are often clear. These are, without a doubt, the very best times to visit the country.
When to go
Without a doubt, the best times to visit Japan are the climatically stable seasons of spring (March to May) and autumn (September to November).
Spring is the time when Japan’s famous cherry trees (sakura) burst into bloom. Starting from Kyūshū sometime in March, the sakura zensen (cherry tree blossom line) advances northward, usually passing the main cities of Honshū in early April. Once the sakura bloom, their glory is brief, usually lasting only a week.
Autumn is an equally good time to travel, with pleasant temperatures and soothing colours; the autumn foliage pattern reverses that of the sakura, starting in the north sometime in October and peaking across most of Honshū around November.
Travelling during either winter or summer is a mixed bag – midwinter (December to February) weather can be cold, particularly on the Sea of Japan coasts of Honshū and in Hokkaidō, while the summer months (June to August) are generally hot and often humid. June is also the month of Japan’s brief rainy season, which in some years brings daily downpours and in other years is hardly a rainy season at all.
Also keep in mind that peak holiday seasons, particularly Golden Week (late April to early May) and the mid-August O-Bon (Festival of the Dead), are extremely popular for domestic travel and can be problematic in terms of reservations and crowds. Likewise, everything in Japan basically shuts down during Shōgatsu (New Year period).
All that said, it is worth remembering that you can comfortably travel in Japan at any time of year – just because you can’t come in spring or autumn is no reason to give the country a miss.