Map showing the annual precipitation, 1961-1990.
Prevailing winds are south-west to westerly bringing moist air masses towards Sweden and the Scandinavian mountains. When air is forced to rise because of the mountains, it is cooled and much of the water in the air is precipitated. Therefore the Norwegian, western side of the mountain range, annually receives large amounts of precipitation, often 2000 to 3000 mm. This large amount of precipitation in combination with low temperatures during summer creates good conditions for the forming of glaciers.
The Swedish west coast is not protected by mountains, and thus the annual precipitation is fairly large and climate maritime. To pass southern Sweden air is forced over the upland parts (Sydsvenska höglandet) like at the Scandinavian mountain range. The effect is similar and the Swedish west coast thus receives the largest amounts of precipitation. The east coast is on the contrary shaded by Sydsvenska höglandet and therefore receives much smaller amounts of precipitation than the west coast.