The short answer is layers, and you already knew that. The longer answer is that San Francisco has the same weather in January and July, a real summer that arrives in September, and a fifteen-degree difference between neighborhoods you can walk between in an hour. Dressing for it is less about the forecast than about knowing which city you'll be standing in at 4 p.m.
Here is how people who live here get dressed.
Why July is cold
From June through August, heat building in the Central Valley pulls ocean air in through the Golden Gate. That air crosses cold Pacific water on its way, condenses, and arrives as the marine layer. The hotter it gets inland, the harder the pull. This is why a heat wave in Sacramento often means a gray, windy afternoon at Ocean Beach.
The pattern breaks in early fall. The ocean has warmed, the valley has cooled, the fog stops rolling in, and San Francisco gets its warmest weather of the year in September and October. Locals call it second summer and plan accordingly.
The numbers, month by month
| Season | Average high / low | What it feels like |
|---|---|---|
| December to January | 57°F / 46°F | Cool, damp, the rainy stretch |
| March to April | 62 to 64°F / 49 to 51°F | Clear mornings, wind by afternoon |
| June to July | 67°F / 53 to 54°F | Fog season. Colder than the number suggests |
| September | 71°F / 56°F | The warmest month of the year |
| October | 69°F / 54°F | Still warm, evenings cool quickly |
Two things the averages hide. The daily range is small, so there is rarely a hot day or a truly cold one. And wind does most of the work: 62 degrees in still sun at Dolores Park and 62 degrees in a gust on the Embarcadero are different outfits.
Dress for the neighborhood, not the city
Temperatures can differ by as much as fifteen degrees across town on the same afternoon.
- The Sunset, the Richmond, Golden Gate Park, Ocean Beach. The west side takes the fog first and keeps it longest. Bring the warm layer even when downtown looks blue.
- Fisherman's Wharf and the northern waterfront. Cooler than inland and exposed to wind off the bay. This is where visitors end up buying an emergency fleece.
- Downtown, North Beach, Union Square. Sunnier and a little warmer, with wind tunnels between the towers.
- The Mission and Noe Valley. Twin Peaks blocks a good share of the fog, so these are reliably the warmest parts of the city. A tee is often enough until sunset.
The three-layer system
Nearly everyone here wears some version of the same thing, year round. The pieces change weight, the logic doesn't.
1. A tee with some substance
Your base layer will spend part of the day being your only layer, so it should hold its shape on its own. A heavyweight cotton tee blocks more wind than a thin one and still looks right when the hoodie comes off at lunch. Ours live in T-Shirts.
2. A long sleeve for the in-between hours
This is the most San Francisco garment there is: more than a tee, less than a sweatshirt, correct from about 10 a.m. to 5 p.m. most days of the year. The Essential Long Sleeve is the plain version. The Above the Fog Long Sleeve and Karl Was Here Long Sleeve are the versions that admit what the weather is doing. The full set is in Long Sleeves.
3. Something heavy for after four
The temperature drops fast when the fog comes back in the late afternoon. A hoodie or crewneck you can tie around your waist is the single most useful thing you can carry. The Essential Grey Hoodie is fleeced and cut boxy, so it layers over a long sleeve without bunching. If you'd rather skip the hood, the Fading Bison Sweatshirt is a washed, oversized crewneck drawn from the herd that has lived in Golden Gate Park since the 1890s. More in Hoodies and Sweatshirts.
From November through March, add a rain shell on top. Skip the umbrella. The wind will take it from you.
What gives visitors away
- Shorts and sandals in July, with nothing else in the bag.
- A brand-new souvenir fleece, purchased under duress at the waterfront.
- A heavy winter coat. It is almost never that cold, and you'll be carrying it by noon.
- Shoes that can't handle a hill. The grades here are real.
Quick answers
Do I need a jacket in San Francisco in summer?
Yes. June through August is fog season, with average highs around 67°F and steady afternoon wind. Bring a sweatshirt or light jacket every day, even if the morning is clear.
What is the warmest month in San Francisco?
September, with an average high of about 71°F. October is close behind. Both are warmer and clearer than July.
What should I wear in San Francisco in October?
A tee or long sleeve during the day, with a hoodie or crewneck for the evening. October afternoons can be warm enough for short sleeves, but it cools quickly after sunset.
Does it rain much?
Nearly all of the year's rain falls between November and March. Summers are dry.
Climate figures are long-term monthly averages for the city; your block may disagree. For why the fog behaves the way it does, the San Francisco Chronicle's explainer on Bay Area summers is worth five minutes. For how it got a name, read The Great Fog Naming Problem.