As suggested by the high-resolution weather prediction models, temperatures surged over eastern Washington on Sunday, at the same time clouds and showers were giving western Washington some relief.
Take a look at the maximum temperatures on Sunday over eastern Washington (below). The entire region was about 100F and MANY locations (dark purples) got above 110F. Stunning.
Here are the max temperatures of 110 and over on Sunday. At least two dozen stations. One observing site (Sunharbor) reported 120F. If true, this would exceed the ALL TIME RECORD TEMPERATURE EVER OBSERVED In Washington (118F in August 1961 at Ice Harbor Dam).
Needless to say, many daily temperature records were broken (record high for June 28). Furthermore, UCANNON RIVER NEAR MARENGO NEAR DAYTON 12NE, WA got to 118F, equalling the all-time record if deemed reliable.
The bottom line: this was one of the warmest days EVER over Eastern Washington. Truly, an historic weather day there.
How much precipitation fell over western--- very light over Puget Sound, but some locations in the Olympics and north Cascades got over an inch (see graphic).