Geography

Downtown San Jose, looking over the Tech Museum and Plaza de César Chávez park. Looking west over northern San Jose (downtown is at far left) and other parts of Silicon Valley. See an up-to-the-minute view of San Jose from the Mount Hamilton web camera

San Jose is located at 37°20′07″N 121°53′31″W / 37.335278°N 121.891944°W / 37.335278; -121.891944. According to the United States Census Bureau, the city has a total area of 180.0 sq mi (466 km2), of which 3.4 sq mi (8.8 km2) (1.91%) is water.

San Jose lies between the San Andreas Fault, the source of the 1989 Loma Prieta earthquake, and the Calaveras Fault. San Jose is shaken by moderate earthquakes, above four on the Richter Scale, on average of one to two times a year. These quakes originate just east of the city on the creeping section of the Calaveras Fault, which is a major source of earthquake activity in Northern California. On April 14, 1984, at 1:15 pm, local time a 6.2 magnitude earthquake struck the Calaveras Fault near San Jose's Mount Hamilton. The most serious earthquake, in 1906, damaged many buildings in San Jose as described earlier. Earlier significant quakes rocked the city in 1839, 1851, 1858, 1864, 1865, 1868, and 1891. The Daly City Earthquake of 1957 caused some damage. The Loma Prieta earthquake of 1989 also did some damage to parts of the city. The other faults near San Jose are the Monte Vista Fault and the Hayward Fault Zone.

Topography

The Guadalupe River runs from the Santa Cruz Mountains (which separate the South Bay from the Pacific Coast) flowing north through San Jose, ending in the San Francisco Bay at Alviso. Along the southern part of the river is the neighborhood of Almaden Valley, originally named for the mercury mines which produced mercury needed for gold extraction from quartz during the California Gold Rush as well as mercury fulminate blasting caps and detonators for the U.S. military from 1870 to 1945. East of the Guadalupe River, Coyote Creek also flows to south San Francisco Bay and originates on Mount Sizer near Henry W. Coe State Park and the surrounding hills in the Diablo Range, northeast of Morgan Hill, California.

The lowest point in San Jose is 13 feet (4 m) below sea level at the San Francisco Bay in Alviso; the highest is 2,125 feet. Due to the proximity to Lick Observatory atop Mount Hamilton, San Jose has taken several steps to reduce light pollution, including replacing all street lamps and outdoor lighting in private developments with low pressure sodium lamps. To recognize the city's efforts, the asteroid 6216 San Jose was named after the city.

San Jose lies close to the Pacific Ocean and close to San Francisco Bay (a small portion of its northern border touches the bay). Santa Clara Valley is the population center of the Bay Area, and like the hub and spokes of a wheel, surrounding communities emanate outwards from the valley. This growth in part, has shaped the greater Bay Area as it is today in terms of geographic population distribution and the trend of suburbanization away from the valley.

There are four distinct valleys in the city of San Jose: Almaden Valley, situated on the south-west fringe of the city; Evergreen Valley to the south-east, which is hilly all throughout its interior; Santa Clara Valley, which includes the flat, main urban expanse of the South Bay; and the rural Coyote Valley, to the city's extreme southern fringe.

Climate A San Jose city street lined with palms.

San Jose, like most of the Bay Area, has a subtropical Mediterranean climate (Köppen Csb). San Jose has 300+ days of sunshine and an annual mean temperature of 60.5 °F (15.8 °C). It lies inland, surrounded on three sides by mountains, and does not front the Pacific Ocean like San Francisco. Because of this, the city is somewhat more sheltered from rain, giving it a semiarid feel with a mean annual rainfall of 15.82 in (402 mm), compared to some other parts of the Bay Area, which can receive about three times that amount.

The monthly daily average temperature ranges from around 50 °F (10 °C) in December and January to around 70 °F (21 °C) in July and August. The highest temperature ever recorded in San Jose was 109 °F (43 °C) on June 14, 2000; the lowest was 19 °F (−7 °C) on December 22–23, 1990. On average, there are 2.7 nights annually where the temperature lowers to or below the freezing mark, and 16 days where the high reaches or exceeds 90 °F (32 °C). Diurnal temperature variation is far wider than along the coast or in San Francisco but still a shadow of what is seen in the Central Valley.

With the light rainfall, San Jose and its suburbs experience about 300 full or partly sunny days a year. Rain occurs primarily in the months from November through April or May. During the winter and spring, hillsides and fields turn green with grasses and vegetation, although deciduous trees are few. With the coming of the annual hot summer dry period, the vegetation dies and dries, giving the hills a golden cover, which unfortunately also provides fuel for frequent grass fires.

Measurable precipitation falls in downtown San Jose on an average of 62 days a year. Annual precipitation has ranged from 6.12 in (155 mm) in 1953 to 32.57 in (827 mm) in 1983. The most precipitation in one month was 10.23 in (260 mm) in February 1998. The maximum 24-hour rainfall was 3.60 in (91 mm) on January 30, 1968. Although summer is normally quite dry in San Jose, a very heavy thunderstorm on August 21, 1968, brought 1.92 in (49 mm) of rain, causing some flooding.

The snow level drops as low as 2,000 ft (610 m) above sea level, or lower, occasionally coating nearby Mount Hamilton, and less frequently the Santa Cruz Mountains, with snow that normally lasts a few days. This sometimes snarls traffic traveling on State Route 17 towards Santa Cruz. Snow rarely falls in San Jose; the most recent snow to remain on the ground was on February 5, 1976, when many residents around the city saw as much as 3 in (7.6 cm) on car and roof tops. The official observation station measured only 0.5 in (1.3 cm) of snow.

Like most of the Bay Area, San Jose is made up of dozens of microclimates. Downtown San Jose experiences the lightest rainfall in the city, while South San Jose, only 10 mi (16 km) distant, experiences more rainfall and somewhat more extreme temperatures.

Climate data for San Jose, California (San Jose Int'l), 1981–2010 normals Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year Record high °F (°C) 79 (26) 81 (27) 87 (31) 95 (35) 101 (38) 109 (43) 108 (42) 105 (41) 104 (40) 101 (38) 85 (29) 79 (26) 109 (43) Average high °F (°C) 58.1 (14.5) 61.9 (16.6) 65.7 (18.7) 69.3 (20.7) 74.3 (23.5) 79.1 (26.2) 81.9 (27.7) 81.9 (27.7) 80.1 (26.7) 74.0 (23.3) 64.3 (17.9) 58.0 (14.4) 70.7 (21.5) Average low °F (°C) 42.0 (5.6) 44.7 (7.1) 46.6 (8.1) 48.6 (9.2) 52.4 (11.3) 56.0 (13.3) 58.1 (14.5) 58.3 (14.6) 56.8 (13.8) 52.5 (11.4) 46.0 (7.8) 41.9 (5.5) 50.3 (10.2) Record low °F (°C) 24 (−4) 26 (−3) 30 (−1) 35 (2) 37 (3) 42 (6) 47 (8) 47 (8) 42 (6) 36 (2) 21 (−6) 19 (−7) 19 (−7) Rainfall inches (mm) 3.07 (78) 3.11 (79) 2.54 (64.5) 1.18 (30) 0.51 (13) 0.10 (2.5) 0.02 (0.5) 0.02 (0.5) 0.18 (4.6) 0.80 (20.3) 1.68 (42.7) 2.61 (66.3) 15.82 (401.9) Avg. rainy days (≥ 0.01 in) 10.2 10.3 9.4 5.6 3.2 0.8 0.2 0.3 1.3 3.2 7.2 10.2 61.9 Source: NOAA Weather.com (record temps)