Seattle’s reputation for frequent precipitation stems from a confluence of geographical and meteorological factors unique to the Pacific Northwest. The city’s location near the Puget Sound, coupled with the presence of the Olympic Mountains to the west and the Cascade Mountains to the east, significantly influences local weather patterns.
The prevailing westerly winds carry moist air from the Pacific Ocean towards the Washington coastline. As this air mass encounters the Olympic Mountains, it is forced to rise, a process known as orographic lift. The rising air cools, causing water vapor to condense and form clouds. This results in substantial rainfall on the windward (western) side of the Olympic Mountains, creating a rain shadow effect on the leeward (eastern) side. However, some moisture still makes its way eastward.