San Francisco is quite a popular summer destination, though travelers should note that summers tend to have much cooler temperatures than other parts of the country. Pack layers (short sleeve shirts, sweaters, jackets) and be sure to always take them with you when you head out to explore the city.
The City by the Bay offers a wealth of sights and activities, especially for first-time visitors. If you’ve never been to San Francisco before, don’t miss the opportunity to take a ride on a cable car. If you’re near the Union Square area, you can hop on one at the Powell Street turnaround and ride over Nob Hill to the Fisherman’s Wharf area. The line to get on the cable car is worth it, but it can be long, so be prepared to wait an hour+.
There are lots of great shops and many food places at Fisherman’s Wharf. After you’ve explored the area a bit, you can catch a ferry to visit the infamous former federal penitentiary, Alcatraz Island. If the weather is clear, the ride will afford you a good view of both the city’s skyline and the Golden Gate Bridge.
If you visit when there’s nice weather, definitely take a bike ride across the bridge, as there are numerous bike rental shops which make it very convenient to rent a set of wheels. Head over to The Haight to explore the epicenter of 1960s San Francisco counterculture and catch a glimpse of the famous Painted Ladies Victorian houses. Or visit Golden Gate Park, which in addition to must-visit permanent attractions such as the deYoung Museum and the California Academy of Sciences, also hosts a number of great summer events, including the Outside Lands Music & Arts Festival (August 9th to 11th in 2013).