Fog is part of daily life in San Francisco from late spring through summer. It can sit over Ocean Beach all day while the Mission is sunny two miles away. Locals even gave it a nickname, Karl. Knowing how it behaves makes it much easier to plan a trip.
In this guide
This guide is part of our San Francisco weather by month hub. For things to do outside, see outdoor activities in San Francisco.
San Francisco fog at a glance
- Peak season June to August
- Clearest months September and October
- Foggiest areas Ocean Beach, the Sunset, the Richmond, the Golden Gate
- Sunnier areas The Mission, Potrero Hill, SoMa, the eastern waterfront
- Daily pattern Thickest in the morning and evening, often thinner at midday
Why San Francisco is so foggy
In summer, cold water along the coast chills the air above it and forms a layer of marine fog. At the same time, the inland valleys of California heat up. The hot air rises and pulls the cool, foggy air in from the ocean through the gaps in the coastal hills. The Golden Gate is the biggest gap, so the fog pours through it and spreads over the western side of the city.
That is why July and August can feel cooler than October. The NOAA averages for the downtown station show highs of about 66°F in July and about 70°F in September and October. Our month pages for July, August and September have the full numbers.
Where the fog goes
The fog usually arrives from the west and moves east. The Outer Sunset and Outer Richmond, near Ocean Beach, are the first to go gray and the last to clear. Twin Peaks and the hills in the middle of the city often stop part of it, so neighborhoods on the east side such as the Mission, Potrero Hill and Dogpatch tend to get more sun.
Where to find sun on a foggy day
Head east. Dolores Park in the Mission is a classic spot to wait out a gray morning. The Embarcadero and the Ferry Building are often brighter than the Presidio. If the whole city is socked in, a trip across the bay to Berkeley or Oakland or north to Napa usually means warmer, sunnier weather.
Seeing the Golden Gate Bridge in fog
Fog can hide the bridge completely, or leave the tops of the towers poking above a white layer. Mornings and late afternoons are often the thickest times in summer. For the best chance of a clear view, try in September or October, or check a live bridge camera before you go. Our Golden Gate Bridge guide lists the viewpoints.
Foghorns
On foggy days you will hear foghorns around the bay. They are navigation signals for ships, and the sound carries across the northern waterfront at all hours when visibility is low.
What to wear
Layers. A day can start at 55°F under fog and climb into the 70s in the sun a few neighborhoods away. A windproof jacket, a sweater and long pants will cover most summer days. See our packing list.
Official resources: National Weather Service San Francisco Bay Area, NOAA U.S. climate normals.
Frequently asked questions
What time of year is San Francisco foggiest?
Summer, from June through August. Fog also shows up in late spring.
Does fog burn off during the day?
Often it thins or pulls back toward the coast by midday, then returns in the late afternoon and evening. Some days it stays all day.
Is it foggy in winter?
Winter has less of the summer marine fog, though you can get ground fog and low cloud on calm mornings, and rain is more common.
Photo credits
Featured image: Frank Schulenburg / Wikimedia Commons, CC BY-SA 3.0; Where the fog goes: Radomianin / Wikimedia Commons, CC BY-SA 4.0.