The climate is a bit differing factor. Where the east side enjoys more sunshine and significantly less rainfall, it also has a much more severe extreme in both the winter and summer months. It get genuinely cold on the east side in the winter. Not quite as bad as say North Dakota, but close you know, like South Dakota ;) Sub zero temps are no stranger to cities like Ellensburg, Pullman, and the inland capital, Spokane. There will also be substantially more snowfall on the eastern side at lower elevations all the way down to sea level. (well 400 feet at least). The eastern two thirds of Washington State is a trade off for hot weather int he summer and cold weather in the winter versus a much more mild range on the west side. The west side will bring rain and some rain, and then after that a bit more rain. But wintertime temps are not likely to stay below freezing for more a than few days at a time and it is very rare to see temps in the single digits and rarer still for sub-zero. Snowfall below 1500 feet tends to be infrequent and short lived, usually. Summers are gloriously mild with dry warm weather that rarely gets hot.
Washington offers a little bit of everything and the whole state remains free of income tax which is the bane of retirees across the land.
