Nybyen has two seasons that matter. From late February to mid-April the sun returns, the snow is deep, and you can take long snowmobile and dog-sled trips across the archipelago — this is the busiest tourist window. From late May to August the sea ice goes and the midnight sun reigns; boats can reach the western fjords, and hiking is possible from Nybyen up to the glaciers.
October to mid-February is polar night: deep cold, no sun, occasional aurora. Quiet, atmospheric, and not for first-timers. Avoid the shoulder weeks in late April and mid-September when half-melted snow makes both summer and winter activities difficult.