You've probably heard that famous line about the coldest winter being a summer in San Francisco. It’s a classic. Even if Mark Twain didn’t actually say it, every person standing on the corner of Powell and Market in a $60 souvenir hoodie they just bought because they’re shivering in July knows the feeling.
Honestly, the temperature in San Francisco in celsius is a bit of a trick question.
If you look at a weather app, it might tell you it's 16°C. That sounds mild, right? But 16°C in the Mission District feels like a glorious spring afternoon, while 16°C at Ocean Beach feels like you’re being slapped in the face by a damp, frozen towel.
The city doesn't have a "climate." It has about twenty of them.
Why the Numbers Lie to You
Most people think of California and imagine palm trees and 30°C heat. San Francisco is the exception that proves the rule.
Basically, the city is a 7-by-7-mile square surrounded on three sides by water. That water—the Pacific Ocean—is cold. Like, 12°C cold. When the inland valleys of California heat up, they suck that cold ocean air in like a giant vacuum.
This creates the "Marine Layer." Or, as locals call him, Karl the Fog.
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Karl is the reason why the average high temperature in July is often only 19°C. Compare that to somewhere like New York or London in the summer, and it sounds downright chilly.
The Real Monthly Breakdown
If you’re planning a visit or just trying to understand the vibe, here is the raw data for the average high/low temperature in San Francisco in celsius.
- January: 14°C / 8°C. This is actually the wettest month. It’s "green" season.
- April: 17°C / 10°C. Spring is beautiful, but don't expect a heatwave.
- July: 19°C / 12°C. The "Cold Summer." This is when the fog is peak.
- September: 22°C / 13°C. This is the secret. September and October are the real summer.
- November: 17°C / 10°C. Things start to cool down and the rains return.
You'll notice the range is tiny. The difference between the "hottest" month and the "coldest" month is only about 8 degrees. It’s a perpetual autumn.
The Microclimate Madness
You can't talk about the temperature in San Francisco in celsius without talking about the hills.
The city has over 40 hills. These hills act as physical barriers. When the fog rolls in through the Golden Gate, it hits the Twin Peaks. It gets stuck there.
This means that on a Tuesday at 2:00 PM:
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- The Richmond/Sunset: It’s 14°C, gray, and misting. You need a parka.
- The Mission: It’s 21°C and people are drinking iced lattes in t-shirts.
- The Financial District: It’s 17°C and wind is whipping through the "canyons" between skyscrapers.
I once walked from the Haight to the Castro—a 20-minute stroll—and watched the thermometer on my phone jump 5 degrees. It’s wild.
What People Get Wrong About "Winter"
The funniest thing about San Francisco is that "winter" is often nicer than "summer."
In January or February, the pressure systems shift. The fog takes a break. You get these crisp, crystal-clear days where the temperature hits 15°C but the sun is so strong it feels much warmer.
The air is cleaner. You can see all the way to Mount Diablo.
Then June hits, and everyone starts complaining again. "June Gloom" is real. Then comes "No Sky July" and "Fogust." If you come here in August expecting a beach day, you’re going to be disappointed.
Survival Tips for the SF Climate
If you want to actually enjoy yourself, you have to dress like an onion.
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Layers aren't just a suggestion; they are a survival strategy. You need a base layer (t-shirt), a middle layer (light sweater or hoodie), and a shell (windbreaker or light jacket).
Don't bother with an umbrella. Seriously. The wind in San Francisco is "sideways" wind. It will break your umbrella in three minutes. Just wear a jacket with a hood.
Actionable Insights for Your Visit
- Check the "Fog Forecast": Don't just look at the temp; look at the wind speed and cloud cover.
- Target September: If you want "warm" (23°C+), book your trip for late September or early October.
- Avoid the Wharf at night: Fisherman's Wharf is right on the water. It is significantly colder than the rest of the city once the sun goes down.
- Stay in the "Sun Belt": If you hate the cold, look for hotels or rentals in the Mission, Noe Valley, or Potrero Hill. They are shielded from the worst of the fog.
Knowing the temperature in San Francisco in celsius is only half the battle. The other half is realizing that the "feels like" temperature is the only metric that matters.
Pack a light jacket. Bring comfortable walking shoes for those hills. And most importantly, don't get mad at Karl—he’s just doing his job keeping the city cool while the rest of the world swelters.
To prepare for your specific travel dates, check the National Weather Service for real-time updates on the marine layer's movement.
Next Steps for You
Check the specific neighborhood forecast for where you're staying, as "San Francisco" averages usually skew toward the colder, foggier airport data rather than the warmer downtown streets.