Here are the observed temperature at Quillayute, Olympia, and Sea-Tac Airport for the past 12 weeks. The average daily highs and lows for the dates are shown by the red and blue lines, respectively. Note how the low temperatures are consistently 5-8F above normal.
To prove this to myself, I decided to have some modeling fun....to play god with the atmosphere! Dave Ovens, who runs the WRF modeling at the UW, took one of our real-time forecasts and replaced the warm sea surface temperatures over the Pacific with the lower climatological sea surface temperatures. Here is the difference in the sea surface temperatures between the two runs we tried, one with the actual warm warm and the other with the normal cooler water (see below) The time for the start of the simulations is 4 PM April 24, 2015.
All we changed was the surface surface temperatures. Here is the difference in surface air temperature for the 168h (7 day) forecast. The temperatures over our region warmed up by 2-3C.
Another contributor to the warmth has been the ridge of high pressure over the West Coast and eastern Pacific--a ridge that has been crazy persistent. And to complete the circle, most of the warm sea surfaces over the eastern Pacific resulted from the high pressure over the West Coast.