San Francisco is located on the West Coast of the United States at the top of the San Francisco Peninsula and includes significant stretches of the Pacific Ocean and Bay Area within its boundaries.

Island as  Alcatraz, Treasure Island, Yerba Buena Island and a small portion of Alameda Island, Red Rock Island, and Angel Island are part of the city. Also included are the uninhabited Farallon Islands, 27 miles offshore in the Pacific Ocena. The mainland within the city limits roughly forms a “seven-by-seven-mile square,” a common local colloquialism referring to the city’s shape, though its total area, including water, is nearly 232 square miles (600 km²).

San Francisco is famous for its hills. There are more than 50 hills within city limits.  Some neighborhoods are named after the hill on which they are situated, including Nob Hill, Pacific Heights, and Russian Hill. Near the geographic center of the city, southwest of the downtown area, are a series of less densely populated hills. Twin Peaks,  a pair of hills resting at one of the city’s highest points, forms a popular overlook spot. San Francisco’s tallest hill, Mount Davidson, is 925 feet high and is capped with a 103 foot tall cross built in 1934. Dominating this area is Sutro Tower, a large red and white radio and television transmission tower.

The nearby San Andres and Hayward Faults are responsible for much earthquake activity, although neither physically passes through the city itself. It was the San Andreas Fault which slipped and caused the earthquakes in 1906 and 1989. Minor earthquakes occur on a regular basis. The threat of major earthquakes plays a large role in the city’s infrastructure development. The city has repeatedly upgraded its building codes, requiring retrofits for older buildings and higher engineering standards for new construction.However, there are still thousands of smaller buildings that remain vulnerable to quake damage.

CLIMATE

San Francisco’s climate is characteristic of the cool-summer Mediterranean climate of California’s coast with mild, wet winters and dry summers. Since it is surrounded on three sides by water, San Francisco’s weather is strongly influenced by the cool currents of the Pacific Ocean which tends to moderate temperature swings and produce a remarkably mild climate with little seasonal temperature variation. Temperatures exceed 75 °F  on average only 28 days a year. The dry period of May to October is mild to warm, with average high temperatures of 64–70 °F  and lows of 51–56 °F. The rainy period of November to April is cool with high temperatures of 56–64 °F  and lows of 46–51 °F . On average, there are 67 rainy days a year, and annual precipitation averages 20.4 inches (518.16 mm).

The combination of cold ocean water and the high heat of the California mainland create the city’s characteristic fog that can cover the western half of the city all day during the spring and early summer. The fog is less pronounced in eastern neighborhoods, in the late summer, and during the fall, which are the warmest months of the year. Due to its sharp topography and maritime influences, San Francisco exhibits a multitude of distinct microclimates. The high hills in the geographic center of the city are responsible for a 20% variance in annual rainfall between different parts of the city. They also protect neighborhoods directly to their east from the foggy and cool conditions experienced in the Sunset District; for those who live on the eastern side of the city, San Francisco is sunnier, with an average of 260 clear days, and only 105 cloudy days per year.