So, you’re looking at the 30 day weather forecast San Diego and trying to figure out if you should pack a swimsuit or a North Face puffer. Honestly, I get it. Predicting San Diego weather for an entire month is like trying to guess which taco shop has the shortest line on a Tuesday—it’s mostly vibes and a little bit of science.
January in San Diego is weird. Everyone thinks it’s eternal summer, but right now, we’re actually in the thick of our "winter." If you can even call 65 degrees winter.
The Reality of the 30 Day Weather Forecast San Diego
Currently, we are transitioning. The National Oceanic and Atmospheric Administration (NOAA) just released an update on January 8, 2026, confirming that the La Niña pattern we’ve been sitting in is finally losing its grip. There’s a 75% chance we’ll hit "ENSO-neutral" conditions by the end of March.
What does that actually mean for your trip?
Basically, it means the atmosphere is a bit of a wildcard. While La Niña usually keeps us dry, this year has already thrown some curveballs with random heavy showers. For the next 30 days, expect a see-saw. One week you’re basking in 72-degree Santa Ana winds that make the air feel like a hair dryer, and the next, you’re dodging puddles in the Gaslamp Quarter.
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Temperatures: The 20-Degree Swing
Don't trust a single high temperature number. In San Diego, the "microclimate" is a very real, very annoying thing.
- Coastal (La Jolla/Mission Beach): Highs will hover around 64°F to 66°F. The ocean is currently a chilly 59°F, which acts like a giant ice pack for the beach.
- Inland (El Cajon/Escondido): You’ll see 70°F or even 75°F during the day, but as soon as the sun dips behind the hills, it plummets to 45°F.
If you are staying downtown, your 30 day weather forecast San Diego shows a remarkably consistent average high of 65°F. But the "lows" are the real story. We’re looking at night-time temperatures hitting 48°F to 50°F through the end of January and early February. That is "San Diego shivering" weather.
Will It Rain? Probably.
February is historically our wettest month. While the first half of January stayed relatively dry despite some cloud cover, the long-range models for late January 2026 suggest a shift.
We are looking at "rainy periods" likely between January 19th and January 23rd. The Old Farmer’s Almanac and local NWS stations are tracking a cool-down during this window. After that, expect a brief sunny break before another round of storms potentially hits in mid-February.
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Rain here isn't like Seattle drizzle. It’s usually a concentrated dump for four hours that floods the 163 freeway and then vanishes, leaving the sky looking impossibly blue.
Why the Forecast Changes So Fast
The "Marine Layer" is the ghost that haunts every San Diego local. It’s that thick, gray blanket of clouds that rolls in from the Pacific.
Even if the 30 day weather forecast San Diego says "Sunny," you might wake up to "June Gloom" in January. This happens when the inland deserts heat up and suck that cool, moist ocean air toward the coast. It usually "burns off" by 11:00 AM, but sometimes it just sits there, being moody, all day long.
The "What to Pack" Crisis
If you’re coming for the next 30 days, ignore the shorts—or at least, don't make them your whole personality.
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- Layers are non-negotiable. A t-shirt for 1:00 PM and a light down jacket for 6:00 PM.
- Water-resistant shoes. San Diego drainage is... let's just say "optimistic." If it rains, the sidewalks become mini-rivers.
- Sunscreen. Even at 64 degrees, the Southern California sun is aggressive. You will get a "cloud-burn" if you aren't careful.
Acknowledging the "Winter" Weirdness
Some people get disappointed because they see 66°F on their phone and think it’s going to be tropical. It’s not. It’s crisp. It’s the kind of weather where you see a tourist in a bikini next to a local in a parka and Ugg boots.
The biggest misconception about the 30 day weather forecast San Diego is that it’s "perfect" every day. The truth? It’s volatile in the winter. We get "Santa Ana" events where the humidity drops to 10% and the fire risk spikes, followed immediately by a frost warning in the valleys.
Actionable Strategy for Your Visit
Check the "Hourly" more than the "Daily." Because the temperature swings so much between 4:00 PM and 7:00 PM, an hourly look-ahead will save you from being stranded in a t-shirt when the ocean breeze kicks in.
If you see "Partly Cloudy" for your dates, plan your outdoor activities (Zoo, Balboa Park) for mid-day. The mornings will likely be foggy, and the evenings will require a sweater.
Watch the swell reports if you're a surfer. The same storms that bring rain usually bring the best winter swells to Black's Beach and Sunset Cliffs. Just wait 72 hours after the rain stops before jumping in the water—urban runoff is a real vibe-killer.
Keep an eye on the transition to ENSO-neutral. If the ocean temperatures start to climb toward an El Niño phase earlier than expected, we might see a much warmer and wetter end to February than the current averages suggest.