I have an ancient answer on a slightly broader question that gets into activities: How did people in medieval Scandinavia survive winter?

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Medieval Scandinavian saints, by and large, perform similar miracles to their continental counterparts: helping the blind to see, the lame to walk, and people with pneumonia to breathe. But some of them also provided an additional service: reversing frostbite. Excavated graves at sites where armies are known to have overwintered also suggest the physical toll of northern winters. But at the same time, the methods medieval Scandinavians developed to adapt to their climate proved fundamental to integrating the territory firmly--irreplaceably--into the reviving European economy and political sphere.

The primary means for keeping warm on an individual level in the Middle Ages was fur. As early as the 8th century, rulers from southern Scandinavia intent on extending their territory northward began extracting payment/tribute from the Sami people who populated the Finland/Russia area in furs. As the European economy perked up, more and more furs ended up traveling south with merchants. In return, Scandinavians imported luxury church goods, cloth (even cloth-manufacturing centers import cloth in the Middle Ages), and above all grain from England. Although Scandinavians grew their own crops for consumption, the supplements from England allowed population growth in the north to occur along with a similar explosion on the continent. Archaeologically, we can see that the extent and sophistication of agriculture in Scandinavia increases dramatically in the 11th-12th centuries.

This development coincides with events to the north and east: more powerful groups in Russia were cutting off Scandinavians' access to the richest fur-producing regions like Karelia. But Scandinavians adapted--and made themselves essential to the continent. Medieval people tried their best to build up supplies of food to last through the winter, and William Chester Jordan's study of medieval famines suggests that by the 14th century some regions were regularly storing up enough food to survive one year of bad harvest without unleashing a famine. Nevertheless, people needed something to store up that would last, and also to acquire new food when they didn't have storage (as in cities). And Scandinavia became, in general, where medieval Europe got its preserved fish.

Cod was of course plentiful to catch off the coasts. But the Arctic climate was also perfect, as it turns out, for drying fish for preservation. Local salt mines also allowed fish to be preserved via salting. So Scandinavia's dried cod and salted herring not only fed its native population through the winters, it also went south and fed the growing continental cities.

Farmers could not farm, per se, in the winter, but there was always work to be done with repairs, hunting, and so forth. We know from excavation of army overwinter camps that, already in the days of Viking raids, people would spend winters in craftwork like metalsmithing. There was also more time for games and playing. Ice skates and skis are ancient as an efficient mode of winter transportation, but the earliest references to ice skating as leisure come from the 12th century. From a bit later, the 16th century, there are descriptions of ice skating races. And there are plenty of medieval illuminations of, you guessed it, snowball fights!

Light for crafting and dice would perhaps have been less of a problem, or at least less of an economic problem, in Scandinavia than to the south. Oil for lamps was readily provided by fish and seal oil, which was another key export for the region.

And--crucially--they spent winters caring for livestock. In fact, thanks to the more or less ready supply of dried fish and the import of grain from England, feeding livestock over the winter was almost more of a challenge than feeding people. In fact, the Norse settlements of Greenland didn't even both growing domesticated crops to feed themselves (although they seem to have picked and eaten local berries). They devoted their energy to producing hay to feed their animals through a winter.

Buckland et al. argue that the Greenland settlements' reliance on domesticated livestock, rather than learning from their contact with North American emigres how to travel further into the ocean to hunt bigger and better whales, proved catastrophic. A series of bad harvests meant the livestock starved, and the settlements were abandoned by the end of the Middle Ages. But in the 12th century, the settlers were still supplying Scandinavia with precious walrus ivory and falcons, which the Scandinavians then traded southward.

And then, of course, there were the Scandinavians who found an alternate solution to the long cold winters. Birgitta Birgersdotter was one of the richest noblewomen in 14th century Sweden, with six children surviving to adulthood, significant charity work in her local community, a profitable and influential position in the household of Queen Christina, and an inheritance deep enough to fund the establishment of a continent-spanning monastic order. In other words, she had it pretty good up north. But once her husband died, Birgitta went on permanent pilgrimage to Rome. She spent the rest of her life there--except when she traveled on pilgrimage to the even warmer Near East.

First and foremost, they would do what Viking Age people did every day, nearly all of them, at every opportunity: spin wool.

Spinning wool to create thread for weaving was the single most time consuming work in a Viking Age household. Everybody, save for the smallest children and the most respected men did that in their free time, and less capable people (cripples, seniors, children, unmarried older women) were specifically tasked with it.

Gathering firewood. This was the second most time consuming work. Heating a VA hut with fire was fairly inefficient, but necessary for survival. This required near constant trips to gather firewood (especially brushwood), peat, animal dung, etc for the fire. A long lasting settlement would soon strip its local forests of all non-essential wood (that was not necessary for building, or for sale). This necessitate longer wood-gathering trips as well as local firewood trade.

Weaving - it took the work of 7 spinners to provide woollen thread for one weaver, but almost every household had a weaver (usually the wife, but men and children could weave as well). During winter, weavers would usually work together in a dug in pithouses that were otherwise used for storage. Cloth was woven, cut, sewn into clothes and older clothes repaired in the winter-time. It was also obviously done year-round, but moreso in the winter/fall.

Repairs - a typical VA household would gather a long list of miscellaneous tools, and gear to be repaired, or replaced. Axes, knives and sickles to be sharpened, hoes handled, shovels steeled, baskets repaired, cauldrons tinkered, animals treated if they were ailing, etc

Brewing Ale - it was a year round activity, usually taking a few weeks between batches, but in the winter it was ramped up due to greater caloric needs of the people. VA ale was not like modern beer, it had weak alcohol content but high caloric content. It could be described best as "sourdough drink", that could be also thickened to make a porrige-like meal.

Preparation for house repairs - no building or repair was done in the winter, as it would risk too much exposure and the building materials of the day would work poorly in sub zero conditions. However, raw materials could be prepared in advance. Shingles could be split , clay could be exposed to crumble (freezing and thawing repeatedly), coniferous trees would be bled and de-branched to create resin/sap infused wood.

Art - long time spent indoor would be utilised to decorate everything from jewellery to everyday items in elaborate patterns. This resulted in a curious trait of Viking art, the so called "horror vacui" - fear of empty (unused) space. Confined to the indoors, and with a limited number of items to decorate, the craftsman (or more often, a bored amateur) would cover an item completely in an elaborate pattern leaving almost no empty space.

Entertainment - numerous archaeological finds prove that the VA people owned and used a wide variety of musical instruments (from rare lyres to simple flutes), and music was a competitive sport in itself. So was singing, or rather sung poetry (melo-declamation). Some forms of it called for elaborate kennings (metaphors) and following a precise meter. It was also a competitive pastime, even up to including boastful or mildly insulting "poetry battles".Games of various kind were also popular, among them dice and hnefetafl (a game similar to checkers) are the most known, but numerous others existed, some of which we have only vague clues (like single game pieces). Last but not least, sex and procreation was a winter pastime for a couple stuck at home.

Religion and spiritual life - we have very little information about it, but we know from the sagas that Jól happened in winter, and was the time where Jólnir (one of the incarnations of Odin) came to visit,the faithful (mentioned in Skáldskaparmál, ), and other gods were invoked then. Over time, it was slowly replaced by Christmas, but we know that in the late Viking Age the two holidays were celebrated side-by-side ( Hollander, M. Lee (Trans.) (2007). Heimskringla: History of the Kings of Norway )

Another thing: I would greatly recommend to you to see the Alone in the Past Project, about an archeologist/reenactor surviving winter in a medieval house, living a 9th century life. Of course, actual VA people would not dare live by themselves but functioned as a family/village, but the principles of everyday tasks needed for winter survival are the same.