Japan is hot in August, whichever way you look at it and wherever you go. But, some places are hotter and more uncomfortable than others. Sapporo, capital of the northern island of Hokkaido, sees an average August high of 79° F (26° C), and a low of 66° F (19° C). The major cities of Tokyo, Osaka, Kyoto, and Fukuoka experience highs around 90° F (33° C), and lows of 77° F (25° C), so even overnight you're going to sweat. Average temperatures in Naha, capital of Okinawa, are the same.
The good news is that even though humidity is high, rainfall tends not to be in August. The exception is when the typhoon season comes a bit early. Japan actually has two wet seasons: the first in June-July, and the second at the end of summer, usually falling in September but sometimes in late August.
Crowds and Costs
Although many international travelers avoid much of Japan in August, this is peak domestic travel time, with schools on vacation. Plus, the important Obon festival falls in mid-August for a few days, and many people take this time off work. In August, families head to beaches, parks, amusement parks, campgrounds, and other places of interests to kids and youngsters, so expect crowds in many places.
Hokkaido is an especially popular summer destination because it's cooler than most other places, and Okinawa is popular for its beaches. If you plan to travel to either of these places, book travel and accommodation as far in advance as possible.
Where to Go
Many places in Japan are likely to be busy throughout August, so it will be hard to avoid crowds at popular attractions throughout the country. But, if you'd like to avoid the busiest crowds, check out the Tohoku region of northern Honshu. It's cooler than southern parts of Honshu, but more easily accessible from Tokyo than Hokkaido. There are many beautiful natural attractions and national parks, and the main city of Sendai may just be Japan's most underrated large city.
August is peak season in Okinawa because of its beautiful beaches, but it's very popular and it's not the only place in the country to find lovely island beaches. Check out the islands of the Seto Inland Sea—between Honshu, Kyushu, and Shikoku—or those off the north, west, and south of Kyushu for some quieter alternatives.
To escape the heat, you'll either need to go north, or go high. Japan is a country with many mountains, so there are many options for the latter. The Japan Alps are a popular hiking destination, running through the middle of Honshu. Nikko and the Nikko National Park are an easy trip from Tokyo, and offer UNESCO World Heritage Sites as well as a cooler climate at altitude.
What to Do
The Mt. Fuji climbing season officially runs from 1 July until 14 September, so conditions in August are usually excellent for the climb. While this is hardly an off-the-beaten-path wilderness experience (there are drinks vending machines near the summit!), it is challenging and shouldn't be taken lightly. Travelers with reasonable fitness and hiking experience will enjoy it most, and the views from the top are worth the effort. If you'd prefer to ease yourself in and take your time with the climb, you don't have to start part-way up the mountain (base 5), as most climbers do. Instead, you can begin further down (from base 0), and walk through the forests and past temples, on the longer, more traditional way to the summit.
Fireworks displays. Through July and August, many cities and towns put on summer fireworks displays. In the larger cities, such as Tokyo, these can be spectacular. Take a blanket to a park or the banks of a river and expect well-managed crowds and fireworks that just keep going on and on. Young women often dress in yukata, summer kimono. Even smaller towns tend to have their own displays.
Natsu Matsuri. Japanese summer festivals, or natsu matsuri, are held in many towns, cities, neighborhoods, and even small local streets throughout the country, all summer long. These usually include traditional dancing, music and costumes, portable shrines, large crowds, and plenty of food and drink. Each festival has some unique and distinctive characteristic. There are many summer festivals held in August, so wherever you travel to you won't be too far from one that could be built into your itinerary. Ask your local specialist if this is something you're interested in experiencing.
Obon. Obon is a three-day festival held in mid-August to honor the dead. Graves are tidied, and people remember their deceased loved ones with offerings of candles. This is one of Japan's most important holidays, and many people take vacation at this time.
Traveling to Japan in August? Check out these great itineraries
Explore Japan's Islands - 10 Days. This itinerary focuses on a side of Japan that few travelers see: the remote islands surrounding the main islands. Stargaze on Hachijojima, admire the volcano on Aogashima, and much more.
Magic of Japan: Tokyo, Kyoto, Hiroshima - 12 Days. Discover both the traditional and modern sides of Japan as you visit shrines and temples, witness technological innovation at an amazing digital art exhibition and attend a crazy robot show.
Explore Japan: Tokyo, Nikko, Hakone, & Kyoto - 10 Days. Along with Tokyo and Kyoto, this itinerary takes you to the beautiful mountainside areas of Nikko and Hakone. The former is a place of much spiritual significance, and the latter is one of the best areas in the country to experience the Japanese hot springs.