Should I visit Japan in the Winter (early to mid January) or Summer (mid May to early June)?

I think winter is better because it's too hot and humid in summer in Japan. But it's up to you.

Japan's climate isn't very great.

Its super hot and humid in the Summer and its very windy and cold in the winter.

So it depends on what you like.

If you can't take the humidity I recommend you going in the winter and if you can't bare the cold, you should go during the summer.

However, in June Japan enters "tsuyu" which is the rainy season.

It basically rains everyday.

And rain in Tokyo is horrible since there are so many people with umbrellas.

Its annoying just to walk outside.

And it gets really humid so if you aren't used to humidity it can also get annoying.

I personally recommend the winter.

Rain during vacations is always not a good option

Japan is proud of its four distinct seasons and each offers something special for the traveler to Japan. My favourite is Spring for the warm temperatures, famous cherry blossoms and lots of fun and festivals. I also like Autumn for its cooler temperatures and the beautiful fall colours which can be seen in the mountains. Winter is the time to go skiing/snowboarding or hot spring hopping and Summer is the time for fireworks and festivals.

The worst time to travel in Japan is Golden Week (April 27 to May 6), which is a collection of four public holidays within a week and a time where everybody goes on vacation both inside Japan and abroad. Trains, hotels and tourist places are extremely crowded during this period and prices are a lot higher than usual making this a bad time to travel in Japan.

Although Japan does get uncomfortably hot and humid in summer, this isn't usually the case until July-September time. Mid May-June is a really nice time to come, as it's quite warm (in Kanto) but not too hot. Of course it depends where you're planning on visiting; Okinawa and Hokkaido have very different weather! If you're planning on visiting Kyoto and Tokyo, for example, then May-June would be best because winter can a bit cold and grey to be honest! If you want to go North and ski then winter is best. Whatever you choose I hope you have a great trip!

Some favour winter and some summer but it is down to your budget. Generally speaking, the rush up to christmas is expensive for flight tickets (and everything else) and prices start to drop after the New year i.e. January onwards. So it just depends on how much you guys cam afford or budgeted for. Play around with dates on comparison sites to get a flavour of things