The Puget Sound region is located in the western half of Washington State in the United States. It runs from the Canadian border south to about 5 miles south of the town of Centralia. You can see it in the picture to the left defined by the yellow line on the map. The Puget Sound Basin is framed by the Cascade Mountains to the east and the Olympic Mountains to the west and in the middle is a vast inland sea called the Puget Sound.
The water in Puget Sound is a key moderating influence on our weather, keeping the temperatures mild year-round. If we didn’t have the Puget Sound, our climate would be more similar to the Willamette Valley directly to the south, except drier because of the drying influence of the mountains. The main difference between the Puget Sound region and the Willamette valley, besides the water of the Puget Sound, is the lack of south facing slopes. Most of the terrain in the Puget Sound was defined by the last ice age as glacier ground down any most of the local hills leaving behind vast hills of debris as they retreated. (The glaciers never made it all the way to the Willamette Valley) The glaciers left behind many hills that run North/South with eastern and western exposures and flat tops. Not the typical southern exposures seen in vineyards in Europe or Oregon. The Skagit and Skykomish valleys are an exception where there is an east/west running river that has some nice southern exposures. Generally, the further you go from the water of the Puget Sound, the warmer it will become in the summer months during the day, but wetter as you move out of the Olympic Mountains rain shadow.
An interesting fact is that if you drew a line on the 47th Parallel through Washington state it would go through France right through the Loire Valley and
Burgundy. Such a northern latitude makes a huge difference with the long sunny days during the summer time giving the vines a lot of solar energy.