CHAPTER FIFTEEN: CALIFORNIA

San Francisco is located California and includes significant stretches of the Pacific Ocean and San Francisco Bay within its boundaries. Several islands—Alcatraz, Treasure Island, and the adjacent Yerba Buena Island, and small portions of Alameda island, Red Rock Island, and Angel Island are part of the city. 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 (282 m) high and is capped with a 103 foot (31 m) tall cross built in 1934. Dominating this area is Sutro Tower, a large red and white radio and television transmission tower.

The San Andreas and Hayward Faults are responsible for much earthquake activity, even though neither 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. San Francisco's shoreline has grown beyond its natural limits. Entire neighborhoods such as the Marina and Hunters Point, as well as large sections of the Embarcadero, sit on areas of landfill. Treasure Island was constructed from material dredged from the bay as well as material resulting from tunneling through Yerba Buena Island during the construction of the Bay Bridge. Such land tends to be unstable during earthquakes; the resultant liquefaction causes extensive damage to property built upon it, as was evidenced in the Marina district during the 1989 Loma Prieta earthquake.

Climate
San Francisco's climate is characteristic of California’s Mediterranean climate with mild, wet winters and dry summers. Since it is surrounded on three sides by water, San Francisco's climate 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. 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, temperatures exceed 75°F 28 days a year.

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 percent 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.

Annual precipitation is about 20.4 inches which occurs mainly during the cooler months of November through April. On average, there are 67 rainy days a year.