Precipitation
San Diego has on average 146 sunny days and 117 partly cloudy days a year. The average annual precipitation is less than 12 inches (300 mm), resulting in a borderline arid climate. Rainfall is strongly concentrated in the cooler half of the year, particularly the months December through March, although precipitation is lower than any other part of the U.S. west coast. The summer months are virtually rainless. Rainfall is highly variable from year to year and from month to month, and San Diego is subject to both droughts and floods. Hurricanes and thunderstorms are very rare. Coastal areas are driest; Cleveland National Forest receives more precipitation, and some inland areas like Laguna Mountains average more than 30 inches of rainfall per year.
At the National Weather Service office, there are an average of 41 days with measurable precipitation. The wettest year was 1941 with 24.93 inches (63.3 cm) and the driest year was 1953 with 3.23 inches (8.2 cm). The most rainfall in one month was 9.09 inches (23.1 cm) in January 1993. The most rainfall in 24 hours was 3.23 inches (8.2 cm) on April 5, 1926.
Read more about this topic: Climate Of San Diego