August is a great time to visit the Ballard Locks. With any luck, you'll see some fish, it's fun to see boats move through the locks, and it's free.
Any of the farmers markets can be fun, too -- Ballard and Fremont both have Sunday Street markets.
If your friend is in town for the first weekend of August there will still be some Seafair events, including fleet week and the Blue Angels.
2014 Bobbin Bramble / Brooks B67
2008 Rodriguez Rainier Mirage / Terry Butterfly Tri Gel
2007 Dahon Speed Pro TT / Biologic Velvet