Climate

 

Cabrillo National Monument is characterized by a Mediterranean climate, which consists of warm, dry summers and cool, wet winters. Mean annual rainfall is 9.5 inches, but ranges annually from 3.4 to 19.4 inches, with most rainfall occurring during winter. The predominate cyclic pattern of dry weather for several years or decades, followed by a shorter period of successive intense rain prone years is driven by the Southern Oscillation (i.e. El Nino/La Nina) and the Pacific Decadal Oscillation. Changes in these ocean-atmospheric conditions position the winter jet stream into a more northerly or southerly position. The latter position typically results in warm, wet winters in San Diego.

San Diego is known for its warm, sunny weather. Mean annual temperature is a comfortable 64°F, though temperatures have slowly increased since the early 1900s. Temperatures along the coast are predominantly regulated by dynamics of the Pacific Ocean throughout the year. However, in the fall, strong high pressure over the desert in conjunction with an incoming low pressure system over the Pacific Ocean can abruptly change the direction of local winds from westerly to easterly. When this occurs, relative humidity drops rapidly, temperatures spike throughout the San Diego area, and strong easterly winds form. These winds, called Santa Ana winds, are a classic example of Foehn winds, which are fairly common in the fall and early winter months across southern California and northern Baja California.