San Francisco Fog Forecast

Will it be foggy today? The quickest answer comes from looking at the fog itself: the Bay Area Fog live map shows current satellite imagery of fog, marine layer, and low clouds over San Francisco and the entire Bay Area, updated about every 10 minutes.

Check the Fog Right Now

Bay Area Fog is a fog tracker, not a forecast model — it shows you where the fog actually is. Open the live fog map and play the timeline loop of the most recent frames. Watching the last couple of hours of motion tells you more about the next couple of hours than most text forecasts: you can see whether the deck is pushing inland, holding at the coast, or breaking up.

What Is the Marine Layer?

San Francisco's famous fog is the visible part of the marine layer: a shallow pool of cool, moist air that forms over the cold Pacific and is trapped near the surface by a temperature inversion. When that air cools to saturation, fog and low stratus form. The gray deck then flows inland through gaps in the coastal hills — most dramatically through the Golden Gate.

The Daily Fog Cycle

On a classic summer day, heat in the interior valleys draws cool ocean air inland. Fog surges through the Golden Gate and over the coastal ridges in the evening and overnight, blankets the west side of the city by morning, then “burns off” — retreating toward the coast — as the sun warms the land through late morning and midday. The hotter it gets inland, the stronger the pull, and the more decisively the fog returns at night.

Fog Season

Coastal fog peaks in summer, roughly May through September, with June, July, and August the foggiest months — locals joke about “June Gloom” and “Fogust.” Winter brings a different kind of fog: radiation (tule) fog that forms inland on clear, calm nights, especially in the valleys.

Will the Fog Burn Off?

It mostly depends on how deep the marine layer is. A thin layer (a few hundred feet) usually burns back to the beaches by late morning. A deep, well-mixed deck can shade the coast all day, keeping the Sunset and Richmond gray while downtown and the East Bay sit in sunshine. On the live map, a thinning deck looks patchy and ragged at its inland edge; a stubborn one stays solid and bright white.

Official Forecasts

For actual predictive forecasts — fog, wind, and temperatures — use the National Weather Service's Bay Area office:

• NWS San Francisco Bay Area (Monterey office)
• NWS point forecast for San Francisco
• NWS coastal waters (marine) forecast

Pairing an NWS forecast with the live satellite fog map is the best of both: the forecast tells you what should happen, the satellite shows you what actually is happening.

Fog FAQ

Is it foggy in San Francisco right now?

Check the live Bay Area fog map — it shows current NOAA GOES-West satellite imagery of fog and low clouds, updated about every 10 minutes, day and night.

Where can I see a live fog map of the Bay Area?

Right here at bayfog.app. During the day the map shows a natural-color satellite composite; at night it switches to an infrared view that reveals fog and low clouds in the dark.

How can I tell if the fog will burn off?

Play the timeline loop and watch the inland edge of the deck. A thinning marine layer turns patchy and retreats west; a deep deck stays solid. For a predictive answer, see the NWS Bay Area forecast.

When is San Francisco foggiest?

Roughly May through September, peaking in June, July, and August. Fog usually arrives in the evening and overnight and pulls back toward the coast during the morning.

What is the marine layer?

A shallow layer of cool, moist ocean air trapped under a temperature inversion. Fog and low stratus form inside it — that's the gray deck that pours through the Golden Gate on summer evenings.

More

Curious how the imagery is made? See how Bay Area Fog works, or head back to the live fog map.