Trying to pick for a trip to Seattle in 2 weeks

I've researched the historical weather data for the area for the month of June. I have a general idea, but what I'm not finding is the unexpected or wild fluctuations in the weather that only the locals know about (it rains for an hour everyday, expect a snowstorm at 2pm, the temp drops 50•F at 5pm, etc...).

What do you locals have to say?