If San Diego weather were a flavor, it’d be vanilla because almost everyone finds it favorable, it’s fairly consistent year-round and from year to year, and there’s nothing really shocking about it. No blizzards, no hurricane-force winds, no monsoons, no polar vortexes. Heck, it’s only snowed five times in 125 years of recordkeeping and that is usually a light immeasurable flurry that lasts for a few minutes at higher elevations. Just like no one says no to a free milkshake simply because it’s vanilla, you’d be hard-pressed to find someone who turns down the chance to vacation (or live for that matter) in a spot that boasts 266 days of sunshine a year and average temperatures in the 70s F. Oh yeah, and the thermometer rarely dips below 45 degrees F, even in the dead of winter, and the average annual rainfall is less than 12 inches.
Technically, it’s categorized as a Mediterranean climate although it tends to be generally more arid and dry than typical cities in the classification because it’s basically a desert with beaches. So summers are less humid and winters are drier and less severe and the proximity to the ocean usually mitigates the heat.
But as you will learn upon spending any time in town, knowing the numbers will only take you so far. The county is large as it goes from Oceanside to the Mexican border and from the beach east into Anza-Borrego Desert State Park and the Cleveland National Forest. Obviously, La Jolla won’t have the same weather as the top of Palomar Mountain at 6,138 feet above sea level. Deciphering the climate and figuring out when to go and what to wear based on that takes a bit more nuance. This guide aims to educate hopeful travelers on the weather basics as well as the more unique concepts of June gloom, El Nino, and the Santa Ana winds.
Fast Climate Facts
• Hottest Month: August (78 degrees Fahrenheit/ 25.6 degrees Celsius)
• Coldest Month: January (42 degrees Fahrenheit/5.6 degrees Celsius)
• Wettest Month: January [2.11 inches]
• Sunniest Month: November (75 percent)
• Windiest Month: April (7 mph)
• Most Humid Months: May-August (all average 74 percent)
• Best Month for Swimming: August (70 degrees Fahrenheit/21 degrees Celsius average ocean temperatures)
Spring in San Diego
Let us start by saying that San Diego is a pleasant place to visit at any point in the year and there are always tourists in town. But as the temperatures start to gradually creep back up and rainfall tapers off in spring, the number of visitors tends to increase whether they are coming for spring break, the start of Major League Baseball season (Go Padres!), super blooms, or simply to escape the still punishing cold back home. But beware of May gray, a predecessor of June gloom caused by a blanket of marine fog hovering over the coast.
What to pack: Depending on where you live, this might feel positively delightful but for the thin-blooded this is most definitely still sweater weather in the day andjacket weather at night. Remember this is a desert so it will always cool off after dark. March ties January for coldest nights of the year. Layering is key.
March: 66 F (19 C) / 42 F (6 C)
April: 68 F (20 C) / 55 F (13 C)
May: 69 F (21 C) / 58 F (14 C)
Summer in San Diego
Summer is peak season in San Diego thanks to the hottest temperatures, warmest ocean water, and fairly frequent sunshine. But don’t come to coastal California in June with plans to tan because of the aforementioned June gloom phenomenon. A marine layer moves in overnight and causes low clouds to hover overhead, darkening skies and blocking out the sun until early afternoon. It can even turn into no-sky July. On the bright side, sometimes it translates to lower lodging prices due to less demand.
What to pack: Itsy-bitsy teenie-weenie bikinis or whatever you feel comfortable in at the beach. Hats, sunglasses, and reef-safe sunscreen are also a must. Shorts and comfortable walking shoes for zoo and theme park visits.
Average Temperatures by Month
June: 71 F (22 C) / 61 F (16 C)
July: 76 F (24 C) / 65 F (18 C)
August: 78 F ( 26 C) / 67 F (19 C)
Fall in San Diego
High temperatures last through October. The Santa Anas, which are extremely dry downslope winds that blow hot air in from the desert all over Southern California, are mostly likely to strike in September. The water is still warm in September so surfing and swimming is still possible.
What to pack: It might seem counterintuitive but pack a hat and sunglasses and November is the brightest month of the year with the sun coming out 75 percent of the time. Don’t forget to pack closed-toe shoes and clothes you don’t mind getting dirty if you plan to drive up to Julian to see autumnal color and pick apples. Again, layering is the best strategy.
Average Temperatures by Month
September: 77 F (25 C) / 65 F (18 C)
October: 75 F (24 C) / 60 F (16 C)
November: 70 F (21 C) / 54 F (12 C)
Winter in San Diego
San Diego at its worst will feel positively balmy to those who hail from locales with ice and snowstorms. The likelihood of rain is greatest December through March, but it even so it rarely pours hard enough or long enough to ruin entire getaways. That said, the entire state experienced more rain than usual in 2017 and 2018. And if it is an El Niño year, all bets are off. El Niño is a natural phenomenon that occurs over the Pacific Ocean every two to seven years scientists when the sea surface temperature rises .9 F for three consecutive months and atmospheric conditions and rainfall patterns shift accordingly. It warms the water and causes a variety of complex weather patterns including increased rain, storms, and flooding to occur across the Americas.
What to pack: A raincoat and an umbrella if your hotel doesn’t provide them. Also throw in a winter fleece, coat, and gloves if your itinerary has you exploring the mountains or state parks in the desert.
Average Temperatures by Month
December: 66 F (19 C) / 49 F (9 C)
January: 65 F (18 C) / 48 F (9 C)
February: 66 F (19 C ) / 50 F (10 C)
Average Monthly Temperature, Rainfall, and Daylight Hours
Mild, consistent weather with minimal rain is what San Diego is all about although, like everywhere else, summers have been growing slightly warmer. Here's what to expect in terms of average temperature (Fahrenheit), inches of rain, and daylight hours throughout the year.
• January: 65 degrees; 2.11 inches; 10 hours
• February: 66 degrees; 1.43 inches; 11 hours
• March: 66 degrees; 1.60 inches; 12 hours
• April: 68 degrees; .78 inches; 13 hours
• May: 69 degrees; .24 inches; 14 hours
• June: 71 degrees; .06 inches; 14 hours
• July: 76 degrees; .01 inches; 14 hours
• August: 78 degrees; .11 inches; 13 hours
• September: 77 degrees; .19 inches; 12 hours
• October: 75 degrees; .33 inches; 11 hours
• November: 70 degrees; 1.10 inches; 10 hours
• December: 66 degrees; 1.36 inches; 10 hours