So the air over us is amazingly warm. And to add to it, the flow aloft is now easterly and thus offshore, which isolates us from the marine influence and produces downslope warming. Here is a plot of the temperatures and winds above Seattle-Tacoma Airport for the past 24 h. (time in UTC on x axis, pressure on y axis, 700 is about 10,000 ft). At 850 hPa, the temperatures have warmed from 4 to 18C, a 14C (25F) jump. Extraordinary.
It is going to burn today. UW Probcast (www.probcast.com) is going for 85F in Seattle. What could modify this warmth is if cooler northerly flow modifies the temperatures at lower elevations...which is possible if the easterly flow is not strong enough. Then we would end up in the upper 70s. Current models tend to mix air in the vertical too much, so they tend to overpredict temperatures in this situation.
So far, temperatures are moderate at low levels because the warm air is above us (see plot), but when that air mixes down, expect temperatures to rocket up. I am looking for my shorts.