Average high in the summer is high 70s here in Berlin, but there are areas in Germany that are warmer. But we do have 80s and 90s here as well. We often get a very stable high pressure area sitting over Germany in the summer and then temperatures around 90 are common and can stay for weeks. On the other hand, we can also get the opposite... Generally July and August are our "rainy season"...
Also you have to consider that we are much further north than the US, Berlin is at 52 degrees north, while the US-Canadian border is at 49 degrees north if I am correct. But the climate is very different, influenced on the one hand by the warm gulf stream coming from the Gulf of Mexico through the Atlantic and then from the East, the dry air from the huge Asian landmass, i.e. Russia and even Blankistan, blowing this hot warm air to us.
I was once for a few weeks in Vancouver in 2003 and everyone said it was a heat wave, but actually I found it very pleasent! I imagine Seattle to be similar to Vancouver?