San Diego enjoys a Mediterranean climate with generally mild, sunny weather throughout the year.
Climate in the San Diego area often varies dramatically over short geographical distances, due to the city’s topography (the Bay, and the numerous hills, mountains, and canyons).
In valleys for instance daytimes are much warmer in summer and nights noticeably cooler in winter.
Average monthly temperatures in San Diego range from 57.3 °F (14.1 °C) in January to 72.5 °F (22.5 °C) in August, although late summer and early autumn are typically the hottest times of the year with temperatures occasionally reaching 90 °F (32 °C) or higher.
The daily temperature ranges are fairly small, only about 15 degrees between the highest and lowest readings, a few miles inland these ranges can increase to 30 degrees or more.
“May gray and June gloom” – a local saying, refers to the way in which San Diego sometimes has trouble shaking off the fog that comes in during those months. A thick “marine layer” cloud cover will keep the air cool and damp within a few miles of the coast, but will yield to bright cloudless sunshine between about 5 and 15 miles inland
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. The summer months are virtually rainless.
“Santa Anas” occurr about 10 days out of the year during September through February as warm winds from the inland deserts bring sometimes hot, but always dry conditions.
Hurricanes are all but improbable even though San Diego is only 3° further north than New Orleans. The waters off the coast of California are significantly colder than in the Gulf of Mexico and western Atlantic and as a result, almost all northbound hurricanes dissipate over Baja California before reaching San Diego.
San Diego rarely suffers snow and ice, typically occurring quite a bit inland from the coast at higher elevations.