The clothing advice for men traveling to Hokkaido during the Golden Week

Because Hokkaido is so huge, there is a gap of temperature between the cities. You can’t wear same clothes when you “go Hakodate and Shiretoko” or “go around whole Hokkaido”. 
I personally think that it’s hard to predict how the weather during the Golden Week would be. When I think about past 10 years, sometimes it snowed, or it got so hot like summer, or temperature changed so much from early Golden Week to late Golden Week as if it changed into a different season.
Therefore, this clothing guide is to prepare for anywhere and any weather. 

For tops, choose something adjustable

Underwear +  long sleeve T-shirts or shirt + outerwear.
This is fine as a basic style in Hokkaido during the Golden Week. Adjust to the temperature by taking on and off these clothes. 
For the materials, cotton or linen is fine. If you feel it’s hot, short sleeve T-shirts and shirts are okay but be aware that it gets pretty cold at morning and night in Hokkaido. You will be comfortable with short sleeves only a few hours during the day. It will be surprisingly cold after 3 or 4 o’clock in the afternoon, so make sure to bring something to put on.
Cardigans are not enough for outerwear. It might be fine during the day but other than that, cardigans are too cold. Bring something like short jackets made with cotton or thick sweaters or nylon jackets.
Also, if you are going to be outside for a long time, wear a vest or fleece material clothes under the nylon outerwear. It will be a safe choice to bring those clothes to prepare for bad weather in eastern and northern Hokkaido.

It’s still too cold for short pants and sandals

The best choice for bottoms is jeans or cotton/linen pants. It’s still cold for short pants so wear leggings under them. Cover the ankles and don’t expose skins. Why? Because it is so cold at morning and night!
Sneakers and deck shoes are fine for shoes. If you choose thick socks, sandals might be okay but I think it is still cold at morning and night, and eastern and northern Hokkaido.
Did this help?
Have fun in Hokkaido!