Climate of San Diego

San Diego predominately has a semi-arid steppe climate (Koppen climate classification) with mild, sunny weather throughout the year. It is said that San Diego has the best year-around climate in the United States. Average monthly temperature are high/low: Jan 65/48, Feb 66/50, Mar 66/52, Apr 68/55, May 69/58, Jun 71/61, Jul 76/65, Aug 78/67, Sep 77/65, Oct 75/60, Nov 70/54 and Dec 66/49. Snow and freezing temperatures are virtually nonexistent in the wintertime, only occurring in inland valleys and not along the coast. Average water temperatures range from 57 degrees in December to 69 degrees in August. The warmest water is usually found in the small coves in La Jolla where it can be around 72 degrees in August and early September.

The average annual precipitation is less than 12 inches, resulting in a borderline arid climate. Rainfall is concentrated in the colder half of the year, particularly the months of December through March (January being the wettest with an average of 2.11 inches), although precipitation is lower than any other part of the west coast. Summer months are virtually rainless. Many times when it rains in the San Diego is for only a few days but can be heavy and some flooding occurs. Thunderstorms are rare with moisture from a weakening tropical storm or hurricane off the Baja Coast moves north into the area.

“May gray and June gloom”, a local saying, refers to the way in which San Diego sometimes has trouble shaking off the marine layer, a cloudy layer typically higher in the atmosphere than fog, that comes in during those months. Temperatures soar to very high readings only on rare occasions, chiefly when easterly winds bring hot, dry air front the inland deserts to the coast that are call “Santa Anas.” The “sea breezes” off the Pacific Ocean are Mother Nature’s air conditioner.

El Nino (ocean waters warmer than normal) and La Nina (ocean waters colder than normal) in the central Pacific Ocean influence storm track of winter storms. El Nino supports a southern latitude storm track and La Nina a northern-latitude storm track. Fortunately, southern California (San Diego) is in the southern-latitudes which makes a long range weather forecast somewhat easier to predict. If the El Nino waters are much warmer than normal, the southern-storm track can be very active with one storm after another for a week to 10 days. The surf is extremely high when this occurs with strong rip currents.