Weather in mid May Kanto region - cold winds?

Hi, we are over for 2 weeks from 8 May going to a mix of places - Chichibu to Kusatsu to Karuizawa to Atami to Shuzenji to Hakone. The weather should be a low of 5 in some places but mainly 15 or so to 20 celsius, so I am in a quandary whether to pack a heavy jacket which will be a pain in the warmer places, or a light jacket with a jumper to go underneath. It depends I think on whether there is likely to be cold winds that time of year. Does anyone know?

Hard to predict but this Saturday in Tokyo it was freezing (not literally but still). Somewhere in the alps it even snowed. You have places such as Karuizawa and Hakone that are known to be colder, so I would come prepared for the 5C you mention in the weather forecast.

Now if you achieve that by multiple layers, Hightech clothes or a regular winter jacket, up to you.

Enjoy!

Perfect. Not a layering kind of guy, it is too hot inside in Japan so I tend to go a tee shirt plus a heavy jacket, so that there is less to take off.

Thanks!

I'm a local who often enjoys walking in nature in similar climate as your destinations, mainly in northern Kanto Region in April, and to me the "light jacket with a jumper to go underneath" sounds good enough. But I would add a pair of gloves and a scarf for your neck, and maybe some warm underwear for safety.

The gloves and scarf can be something very thin, and they would make a huge difference, even in the city when air-conditioning happens to become harsh. I usually don't need the warm underwear, but I just make sure I have enough warm socks and disposable warmers (that are also available at drug stores in Japan). Needless to say, I'd always cover my legs in that climate.

This will be a slightly different story if you are planning to do some serious hiking. You should carry a portable raincoat, and your shoes should be something you can wear in rain and mud. In fact, even if you're not hiking, you are going to places with a lot of great nature, so you should make sure you wear sporty shoes. And a portable plastic raincoat does help when there is some unexpectedly cold wind.

I highly doubt you'd need bulky things like down jackets, but again, that depends on what activities you are doing. Note that tourists in your destinations would typically stay indoors after dinner and enjoy some onsen or go to bed early.

Your last sentence describes us perfectly

I don't think you need a winter bulky jacket. As they said, you just need a thin-layering. It's very convenient to travel around...
in my opinion, for your option of wearing t-shirt and thick jacket = you will experience "too hot" and "too cold"

Cheers, yes I picked up my heavy one last night and figured it must weigh over a kg and is very bulky as against barely noticing the weight of a light one. Light one it is.

Last trip (October/Nov last year) I took the heavy one which was handy for a few days when it snowed at Kamikochi, but then I had to lug it around through high 20's celsius in Kansai and 30's in Taipei.

Definitely some sort of light windbreaker/waterproof jacket with jumper or fleece and then whatever regular clothes you'd wear under that, IMHO. Less bulk, less weight, more flexibility.

For some days you'll want all the layers; for others you'll just want the jumper or the light jacket and can leave the other one behind.

If things get really cold, there's always Uniqlo for a set of cheap thermals...