San Francisco occupies the tip of a peninsula halfway up the coast of northern California, surrounded on three sides by bodies of water: the Pacific Ocean, the Golden Gate strait, and the San Francisco Bay. The city is laid out in a grid over some 40 hills, reaching heights of nearly 1,000 feet; this sometimes causes wide variations in temperature and sky conditions in different areas of town. The Pacific air keeps the temperatures generally moderate, rarely ranging above 75 degrees or below 45 degrees, leading San Francisco to be called "the air-conditioned city." The climate is very similar to coastal areas on the Mediterranean.
Although temperatures remain relatively constant, there are two definite seasons—wet and dry—with more than 80 percent of annual precipitation taking place between November and March. Perhaps the most distinctive feature of the local climate is the banks of fog that can roll in off the ocean, quickly covering various areas of the city, and then disappear just as quickly. The fog is most common on summer mornings, coming off the cooler ocean and backing up against the hills, but it also comes from the colder inland areas during the winter. The fog affects different elevations in varying amounts, covering the city in complex patterns of fog and sunshine.
Area: 47 square miles (2000)
Elevation: 155 feet above sea level
Average Temperatures: January, 52.3° F; August, 62.4° F; annual average, 58.6° F
Average Annual Precipitation: 22.1 inches