The summers in Scandinavia are temperate with the average temperature staying around 15C/60F which isn't exactly the warmest, so to what extent did life change from the harsh winters?
The Scandinavian log cabins were well designed to surviving the harsh winters, and with a practically limitless supply of timber the stove in the house could always be lit and life centred around this stove. But as the weather got warmer did life continue to be mostly lived inside, or was it moved outside leaving the house just to be slept in?
Did diets drastically changed? I know they consumed a lot of salted or smoked fish and meat like lutefisk and root vegetables in winter, but did this vary when to came to summer?
Finally there has been some discussion into how raiding patterns changed throughout the year, with more raids in summer and rarely any in winter. I can't seem to find any good sources on this, and would be interested in reading more into it
Geography. Scandinavia is really quite a temperate and hospitable region. The territory that the vikings settled in the middle of the Atlantic may have been on the absolute limit as to where agriculture is possible (especially Greenland), but the idea that the Norse homelands were in anyway infertile is just plain wrong.
Climate history. It is equally wrong to believe that the vikings lived during an especially cold period. The era around ca. 800 AD was indeed quite cold, but the mean temperature only rose from then until the 13th century, forming what's termed The Medieval Warm Period. It was a much warmer period than the following era, The Little Ice Age, which reached a record low during the 17th century.
Diet. The absolutely most common crop during the viking age was barley, being either consumed in the form of bread or as a grain paste. Barely was also used in the brewing of beer, which made it even more important. And while the rye had already reached Denmark and oats had special place on the Swedish west coast, barely stood in class all of its own when it comes t Scandinavian crops. We actually have a few badly worn, but preserved breads from the viking age, but I've yet to find a scientist who can tell if a 1000 year old bread was prepared during summer or winter. But one thing I can tell is that it the animal slaughter was done during the fall, when the animals were at the fattest. So you'd probably see more meat during winter.