Contrary to popular belief.... Seattle is not even close to one of the rainiest places in the country. In fact, Seattle typically sits around 32nd to 44th position for total rainfall. The reputation for being the rainy city comes primarily due to the total amount of rainy days [around 150 a year].
All of that being said, from July through September Seattle typically sees very little rain and the temperature typically falls between 70-90 F or 21-32 C.