The following are a variety of meteorological effects which affected the Vikings, some directly some indirectly:

Magnetic Storms:
Vary in intensity and frequently with the sunspot cycle, similarly to the aurora. Magnetic storms vary greatly in duration from a few hours to several days. A wide variety of optical phenomena such as mirages, green flashes, solar arcs, halos,coronas, ice blinks, land blinks, aurora borealis, and St. Elmo’s fire are observed in these waters.

Sunlight Hours:
At many points in Northern Scandinavia the possible duration of sunshine is considerably reduced because of the screening effect of the mountains and hills. Hence, the possible duration of sunshine in many Norwegian valleys and Fjords for instance is less than 55% of what it could have been by free horizon or lack of topographical blocks.