Western Washington. Try the Bellingham area (Birch Bay). We spend several weeks there every summer, you can do day trips all over the place (Mt Baker, San Juan Islands, Vancouver BC). Olympic Peninsula is another good place for exploring and doesn't get to warm. And the Oregon coast is great - - just get somewhere before the holiday weekends, but otherwise cool. Long Beach in Washington state is a good place to explore. And then there is Mt. Rainer/Mt. St Helens (stay in Randall, WA and see both), Mt. Hood. Even Eastern Washington, which gets hot in the summer, will be better than being in AZ for June-August.
