I believe the probability of a warm summer in the Pacific Northwest is quite high.
Let me tell you why.
During the summer, high pressure builds offshore (the East Pacific High) and marine air from off the eastern Pacific Ocean slowly moves into the Pacific Northwest. The temperature of the ocean surface is an important factor in controlling our surface air temperature (and dew point).
For many months, the sea surface temperature (SST) of the eastern Pacific has been above normal and that is certainly true today. Here is the sea surface temperature anomaly (difference from normal) for the past week. You can see a huge area of warm water off the west coast of North America, with the water temperatures being 3-3.5 C (5-6F) above normal. There is no reason to suspect this warm water anomaly won't persist into the summer, and as the air moves over the warm water its temperaturs will be enhanced.
In fact, the latest runs of the NOAA Climate Forecast System (CFS) model suggests a continuation of the warm water off our coast into the summer.
So the existence of the warm water alone suggests a warmer than normal summer.
But what does the NOAA CFS forecast for summer air temperatures look like? Here is the answer for June-July and August. Substantially warmer than normal!
The official NOAA seasonal temperature probability forecast? Warmer than normal over the Northwest, of course.
Seasonal forecasts have an imperfect track record, with some major busts in recent memory. But making use of all the tools my profession has available, it does appear that the probabilities are strongly weighted towards another warm summer here in the Pacific Northwest. I haven't discussed precipitation , but similar guidance does not suggest an usually wet or dry warm season.
What are the implications of the upcoming warm summer? A longer hiking season for sure. Increased chances of wildfires. Higher summer humidity. A better beach season than normal. Another great tomato growing season. Less chance of spring freezes in eastern Washington. And much more. I enjoy a warmer summer even though it may not be politically correct to say it.