i used to live in tacoma washington. while i didnt fly their all i can tell you is it does "rain" quite a bit in the winter/spring. however i wouldnt really call it rain (im in kansas now when it rains if your outside for 30 seconds your soaked, while in washington if it rains you could be out for a few hours and get damp" the question is would you mind flying in a small drizzle. (build some spad's, use a few old engines and dont worry about it)
but during the summer/fall its rarly above 95 degrees (would be great weather to fly in), during the winter its usually about 40 degrees (very flyable) and from what i remember their is not usually wind (could be wrong since wind doesnt affect much when you arnt flying so you dont pay much attention to it) although their are a few "wind storm" through the year