You’ve probably seen the postcards. Golden Gate Bridge bathed in orange sunlight, cable cars climbing hills under a cloudless blue sky, and people wearing sundresses in Union Square. It looks like a Mediterranean dream.
Then you actually get here in July and realize you're shivering.
The monthly weather for San Francisco is, quite frankly, weird. It doesn’t follow the rules that govern the rest of North America. While the East Coast is sweltering and Los Angeles is baking, San Francisco is often huddling under a thick, wet blanket of gray fog that locals affectionately (and sometimes bitterly) call Karl.
If you pack shorts for a summer trip to the City by the Bay, you’re basically donating $60 to the local economy because you’ll be forced to buy an overpriced "I Heart SF" hoodie at Fisherman’s Wharf within three hours of landing. I’ve seen it happen a thousand times.
The Microclimate Reality
San Francisco is a seven-by-seven-mile square of chaos.
Because of the topography—all those famous hills—and the proximity to the Pacific Ocean, the weather can change drastically in the span of four blocks. This isn't an exaggeration. You can be sweating in the sun in the Mission District, walk twenty minutes toward the Richmond, and find yourself in a misty wind tunnel that drops the temperature by 15 degrees.
The Pacific Ocean stays cold. Always. It hovers around 54 to 58 degrees. When the inland valleys of California heat up, that hot air rises, creating a vacuum that pulls that cold, moist Pacific air through the Golden Gate. That’s the "marine layer." It’s a giant natural air conditioner that never turns off.
Breaking Down the Calendar
January and February: The Real Winter
Honestly, January is often clearer than July.
This is when the city gets most of its rain. Thanks to atmospheric rivers—huge plumes of moisture from the tropics—San Francisco can go from a crisp, sunny 60-degree day to a torrential downpour that floods the Embarcadero. January averages about 4.5 inches of rain.
Temperatures usually sit between 46°F and 58°F. It’s chilly, but it rarely freezes. You’ll see the hills of the Bay Area turn a neon green that looks almost fake. If you’re visiting now, bring a real raincoat, not just a windbreaker.
February starts to feel like spring. You get the "false spring" where the plum blossoms bloom, and for three days, everyone thinks winter is over. It’s a lie, but it’s a beautiful one.
🔗 Read more: Woman on a Plane: What the Viral Trends and Real Travel Stats Actually Tell Us
March and April: The Windy Transition
March is hit or miss. You might get a week of 70-degree weather, or you might get hammered by the tail end of the rainy season.
By April, the rain starts to taper off, but the wind picks up. The "breeze" off the bay can be brutal. If you’re planning on walking across the Golden Gate Bridge in April, tie your hair back and wear layers. The wind chill makes 60 degrees feel like 45.
May and June: The Arrival of "June Gloom"
This is where the confusion starts for visitors.
Late May brings the start of the heavy fog. In most of the world, June means summer has arrived. In San Francisco, June means the sun disappears. The fog rolls in during the late afternoon and often doesn't burn off until noon the next day. Sometimes, it doesn't burn off at all.
Local meteorologists at stations like KRON4 or ABC7 often have to explain to frustrated tourists why it’s 95 degrees in San Jose and 55 degrees at Ocean Beach. It’s the pressure gradient. The hotter the Central Valley gets, the thicker the fog becomes.
July and August: "Fogust"
August is the coldest month for many parts of the city.
Mark Twain probably never actually said the famous quote about the coldest winter being a summer in San Francisco, but whoever did say it was spot on. July and August are dominated by the marine layer.
If you go to a Giants game at Oracle Park in July, you’ll see people wrapped in blankets. The "monthly weather for San Francisco" during these months is famously disappointing for beach-goers.
Average highs are technically around 67°F, but that’s a deceptive number. It’s often cloudy and damp until 2:00 PM, sunny for three hours, and then the wind starts howling again at 5:00 PM.
September and October: The Real Summer
If you want the weather you saw on the postcards, come now.
💡 You might also like: Where to Actually See a Space Shuttle: Your Air and Space Museum Reality Check
September and October are the warmest months in San Francisco. The inland valleys start to cool down, which weakens the vacuum effect that pulls in the fog. The offshore winds start to blow from the east, pushing the marine layer back out to sea.
This is when we get our heatwaves. It’s not uncommon to see 85 or even 90 degrees in early October. The city feels alive. Everyone is outside because we know the rain is coming back soon. This is the best time for outdoor dining in North Beach or a picnic in Dolores Park.
November and December: The Descent into Dampness
November is a toss-up. It can be gorgeously crisp and clear, or it can be the start of the gray season.
By December, the days are short and the air is damp. It’s not the bone-chilling cold of Chicago, but a "wet cold" that sinks into your skin. You’ll want a wool coat and a sturdy umbrella.
The Wardrobe Strategy (Because You'll Need One)
You have to dress like an onion.
Standard San Francisco attire is a base layer (t-shirt), a middle layer (flannel or light sweater), and an outer shell (Patagonia nano-puffs are basically the city uniform for a reason).
You will be taking these layers off and putting them back on all day long. If you're in the Sunnyside neighborhood, you're in a t-shirt. If you take the Muni to the Sunset District, you're putting that jacket back on before you step off the train.
Rainfall Patterns and the Drought Cycle
San Francisco has a Mediterranean climate, which means we have a very defined wet season and dry season.
Between May and September, it almost never rains. Like, literally zero inches. This is why the hills turn brown (or "golden" as the marketing people say) by July.
The rain usually arrives in late October or November. Recently, we’ve been seeing more "all or nothing" years. Some years we have a "Ridiculously Resilient Ridge" of high pressure that blocks all rain, leading to droughts. Other years, like the winter of 2023, we get hit by dozens of atmospheric rivers that dump a year's worth of rain in three weeks.
📖 Related: Hotel Gigi San Diego: Why This New Gaslamp Spot Is Actually Different
Specific Tips for Travelers
Don't trust the iPhone weather app.
Seriously. The default weather app usually pulls data from a sensor at the San Francisco International Airport (SFO), which is 13 miles south of downtown, or from a station in the middle of the city. It doesn't account for the microclimates.
I recommend using an app like Weather Underground and looking at the "Wundermap." You can see the real-time temperature sensors in different neighborhoods. You'll often see 72 degrees in the Potrero Hill and 58 degrees at the Cliff House at the exact same moment.
If you are planning a trip, here is a quick cheat sheet for what to expect based on the monthly weather for San Francisco:
- Best for photos: September and October. The air is clear and the sun is out.
- Best for budget: January and February. Hotels are cheaper because people are afraid of the rain, but you often get stunning clear days between storms.
- Most deceptive: June and July. Do not bring a swimsuit unless your hotel has a heated indoor pool. You will not be swimming in the ocean unless you have a 5mm wetsuit and a death wish.
- Best for hiking: April and May. The wildflowers on Mt. Tamalpais (just across the bridge) are incredible, and the air is cool enough that you won't overheat.
Navigating the Wind
The wind is the silent killer of outdoor plans.
In the late afternoon, the wind usually kicks up from the West. If you’re planning a sunset cruise on the Bay, double whatever layers you think you need. The wind on the water is relentless. Even on a "warm" day, the combination of 15mph winds and 55-degree water makes the deck of a boat feel like an icebox.
Why the Fog Matters
The fog isn't just weather; it's the city's lungs.
It keeps the giant Redwoods in the nearby Muir Woods alive during the dry summers. They actually "drink" the fog through their needles. It also keeps the city's energy bills lower than almost anywhere else in California because very few people actually need air conditioning.
When the fog rolls in through the Golden Gate, it’s a physical thing. You can watch it pour over the Twin Peaks like a slow-motion waterfall. It’s beautiful, provided you have a sweater.
Actionable Steps for Your Visit
- Check the Fog Bridge webcam before you head to the Golden Gate Bridge. There is nothing more disappointing than paying for an Uber to the bridge only to find you can't even see the towers through the white-out.
- Stay in the "Sunbelt" neighborhoods if you hate the cold. Look for accommodations in the Mission, Potrero Hill, or Dogpatch. These areas are shielded by the hills and get significantly more sun than the western side of the city.
- Always carry a scarf. It’s the easiest way to regulate your temperature when the wind kicks up unexpectedly.
- Avoid the "June Gloom" trap. If you are visiting California for a beach summer, go to San Diego. If you are coming to San Francisco, come for the food, the culture, and the moody, atmospheric vibes.
- Watch the barometric pressure. If you see a rapid drop in winter, get off the roads. San Francisco's drainage systems can struggle with "Pinedrop" events (intense rainfall), and the hills become slick very quickly.
The monthly weather for San Francisco is a lesson in contradiction. It’s a place where you can get a sunburn and a chill in the same afternoon. But once you understand the rhythm of the fog and the logic of the microclimates, it’s one of the most comfortable and predictable climates in the world. You just have to play by its rules.
Go get yourself a good windbreaker and a local sourdough bread bowl. You’ll be fine.