In the summer, San Francisco is cold. Gray and Cold. Drive one hour outside the city and you'll find 100+ degree temperatures. When sun and a little adventure is what you're craving, try a whitewater rafting trip on the American River. Part of the trip is leisurely. As you paddle, you'll pass golden hills, pine forests, and the place where gold was discovered - Sutter's Mill. Pay attention though, there are several grade three rapids, including one named "Bouncing Rock," which may bounce you into the turbulent water (This may or may not have happened to me). Don't forget to keep paddling.