It is highly recommended to visit Hokkaido at any time of the year, however if you have no choice but in winter time, here are a few recommendations to enjoy!
Of course it is interesting to visit the city of Sapporo as you can see a lovely botanic garden, or spend some time in the wonderful Odori Park. Nonetheless, in winter it is breath-taking to visit the Snow Festival! You can enjoy amazing snow sculptures! It usually starts in the beginning of February and if you manage to go there you will definitely think that it is purely art!
As winter is of course very cold you should visit indoor places and one of our recommendation is the Sapporo beer museum! Indeed, you can learn more about beer and brewing and of course you can have a few beers there.
After that, you should definitely go to Noboribetsu area which is the most famous hot spring resort of Hokkaido! There are various types of hot spring water which are considered to be some of the best in Japan! Moreover, the hot spring town is quite small but full of comfortable hotels and it is easily accessible by bus from Noboribetsu station.
You can also visit Hakodate which is a city that offers great fresh seafood and if you go to the mountains you will get an amazing view of the city. Moreover, if you are interested in history, you should go there because there are plenty of historical places to visit such as the Fort Goryokaku or the Motomachi.
Our last recommendation is to visit Daisetsuzan National Park which is located in the center of Hokkaido and offers stunning mountain scenery and a few hot springs. It is a great area for hikers, however, you should be cautious about the deer and brown bears. The easiest accessible peak is that of Mount Kurodake.