Berkeley, California - Climate

Climate

Berkeley has a cool summer Mediterranean climate (Köppen climate classification Csb), with dry summers and wet winters. The summers are cooler than a typical Mediterranean climate thanks to upwelling ocean currents along the California coast. These help produce cool and foggy nights and mornings. Berkeley's location directly opposite the Golden Gate ensures that typical eastward fog flow blankets the city more often than its neighbors.

Winter is punctuated with rainstorms of varying ferocity and duration, but also produces stretches of bright sunny days and clear cold nights. It does not normally snow, though occasionally the hilltops get a dusting. Spring and fall are transitional and intermediate, with some rainfall and variable temperature. Summer typically brings night and morning low clouds or fog, followed by sunny, warm days. The warmest and driest months are typically June through September, with the highest temperatures occurring in September. Mid-summer (July–August) is often a bit cooler due to the sea breezes and fog common then.

Average January temperatures are a maximum of 56.4 °F (13.6 °C) and a minimum of 43.6 °F (6.4 °C). Average September (the warmest month) temperatures are a maximum of 71.7 °F (22.1 °C) and a minimum of 55.9 °F (13.3 °C). In a year, there are an average of 2.9 days with highs of 90 °F (32 °C) or higher, and an average of 0.8 days with lows of 32 °F (0 °C) or lower. The highest recorded temperature was 107 °F (42 °C) on June 15, 2000, and the lowest recorded temperature was 24 °F (−4 °C) on December 22, 1990.

January is normally the wettest month, averaging 5.13 inches (130 mm) of precipitation. Average annual precipitation is 25.40 inches (645 mm), falling on an average of 63.7 days each year. The most rainfall in one month was 14.49 inches (368 mm) in February 1998. The most rainfall in 24 hours was 6.98 inches (177 mm) on January 4, 1982. Light snow has fallen on rare occasions. Snow has generally fallen every several years on the higher peaks of the Berkeley Hills.

In the late spring and early fall, strong offshore winds of sinking air typically develop, bringing heat and dryness to the area. In the spring, this is not usually a problem as vegetation is still moist from winter rains, but extreme dryness prevails by the fall, creating a danger of wildfires. In September 1923 a major fire swept through the neighborhoods north of the University campus, stopping just short of downtown. (See 1923 Berkeley fire). On October 20, 1991, gusty, hot winds fanned a conflagration along the Berkeley–Oakland border, killing 25 people and injuring 150, as well as destroying 2,449 single-family dwellings and 437 apartment and condominium units. (See 1991 Oakland firestorm)