Big Sur - Climate

Climate

Big Sur typically enjoys a mild climate year-round, with a sunny, dry summer and fall, and a cool, wet winter. Coastal temperatures vary little during the year, ranging from the 50s at night to the 70s by day (Fahrenheit) from June through October, and in the 40s to 60s from November through May. Farther inland, away from the ocean's moderating influence, temperatures are much more variable. The weather varies widely due to the influence of the jagged topography, creating many microclimates. This is one of the few places on Earth where redwoods grow in close proximity to cacti.

The official National Weather Service cooperative station at Pfeiffer Big Sur State Park reports that January is the coolest month with an average maximum of 60.0 °F (15.6 °C) and an average minimum of 43.2 °F (6.2 °C). August is usually the warmest month, with an average maximum of 77.3 °F (25.2 °C) and an average minimum of 50.2 °F (10.1 °C). The record maximum temperature was 102 °F (38.9 °C) on June 20, 2008. The record minimum was 27 °F (−2.8 °C), recorded on December 21, 1998, and January 13, 2007. There are an average of 8.8 days annually with highs of 90 °F (32 °C) or higher and an average of 1.4 days with lows of 32 °F (0 °C) or lower. Average annual precipitation at the state park headquarters is 41.94 inches (1,065 mm), with measurable precipitation falling on an average of 62 days each year. The wettest year was 1983 with 88.85 inches (2,257 mm) and the driest year was 1990 with 17.90 inches (455 mm). The wettest month on record was January 1995 with 26.47 inches (672 mm) and the most precipitation in 24 hours was 9.23 inches (234 mm) on January 31, 1963. More than 70% of the rain falls from December through March, while the summer brings much drier conditions. Measurable snowfall is rare in coastal Big Sur, with the maximum monthly snowfall of only 1.0 inch (25 mm) recorded in December 1932, but is common in the winter months on the higher ridges of the Santa Lucia Mountains. The abundant winter rains cause rock and mudslides that can cut off portions of Highway 1 for days or weeks, but the road is usually quickly repaired.

Farther to the south, near San Simeon, weather records were kept at the Piedras Blancas Light lighthouse until 1975. Based on those records, January was the coldest month with an average maximum of 58.6 °F (14.8 °C) and an average minimum of 45.3 °F (7.4 °C). September was the warmest month with an average maximum of 64.2 °F (17.9 °C) and an average minimum of 51.9 °F (11.1 °C). Temperatures rarely reached 90 °F (32 °C) or higher, occurring only 0.1 day annually; nor dropped to 32 °F (0 °C) or lower, occurring only 0.5 day annually. The highest temperature recorded was 91 °F (33 °C) on October 21, 1965. The lowest temperature recorded was 29 °F (−2 °C) on January 1, 1965. Annual precipitation averaged 20.28 inches (515 mm). The wettest year was 1969 with 41.86 inches (1,063 mm) and the driest year was 1959 with 9.71 inches (247 mm). Measurable precipitation fell on an average of 48 days annually. The most rainfall in one month was 18.35 inches (466 mm) in January, 1969, including 5.28 inches (134 mm) in 24 hours on January 19. Today, weather records are kept at the park headquarters at San Simeon and published in some newspapers.

Along with much of the central and northern California coast, Big Sur frequently has dense fog in summer. The summer fog and summer drought have the same underlying cause: a massive, stable seasonal high pressure system that forms over the north Pacific Ocean. The high pressure cell inhibits rainfall and generates northwesterly air flow. These prevailing summer winds from the northwest drive the ocean surface water slightly offshore (through the Ekman effect) which generates an upwelling of colder sub surface water. The water vapor in the air contacting this cold water condenses into fog. The fog usually moves out to sea during the day and closes in at night, but sometimes heavy fog blankets the coast all day. Fog is an essential summer water source for many Big Sur coastal plants. Most plants cannot take water directly out of the air, but the condensation on leaf surfaces slowly precipitates into the ground like rain.