Western Washington is known as having a far wetter climate than the eastern portion of the state, primarily due to the effects of the Cascades' rain shadow.

[1] The average location in Western Washington gets 168 days of measurable precipitation per year.

[2] The place that receives the most recorded precipitation is Lake Quinault on the Olympic Peninsula, with an average of 332.92 centimetres (131.07 inches) per year.

[3] The Long Beach Experimental Station has the most days of measurable precipitation, averaging 215 each year.

[2] As of the 2020 census, Western Washington was home to 6,037,688 of the state's total 7,705,281 residents, making its population comparable to that of Missouri.