Why is western Norway wetter than eastern Norway?

Western Norway is significantly wetter than eastern Norway primarily due to the country's topography and its position in the path of North Atlantic weather systems.

Norway lies directly in the path of North Atlantic cyclones, which bring frequent precipitation to the region. Western Norway, or Vestlandet, experiences a marine climate characterized by high annual precipitation, reaching nearly 90 inches (2,250 mm).

In contrast, eastern Norway, or Østlandet, is sheltered from these moisture-laden winds by a complex of mountain ranges, including the Lang Mountains. These mountains act as a barrier, causing the eastern region to have an inland climate with significantly less annual precipitation—typically less than 30 inches (760 mm).12