LOCATION · United States
San Francisco Weather Radar & Live Satellite Map
Is that fog, an atmospheric river, or wildfire smoke over the Bay right now?
San Francisco has some of the most distinctive weather of any major city — and almost none of it is ordinary rain. The Bay Area's grey skies come in three completely different flavours: the summer fog that locals nicknamed "Karl," the wildfire smoke that drifts in each autumn, and the winter atmospheric rivers that deliver nearly all the year's rain in a few dramatic bursts. Telling them apart is the whole game here, and it's what the map is built to do.
The fog: a coastline running its own air-conditioner
The summer fog is the Bay Area's signature. It's driven by a beautiful piece of natural machinery: the hot Central Valley inland heats up and draws air in off the ocean, and the Pacific right offshore is unusually cold — chilled by upwelling that brings deep, cold water to the surface. That cold sea condenses the incoming air into a low deck of fog, which floods through the Golden Gate and over the hills, especially in the afternoon and evening, then often burns back by midday.
On the satellite layer it's unmistakable once you know it: a smooth, featureless grey sheet pinned to the coast and pouring inland through the low gaps, nothing like the lumpy, towering cloud of a storm.
The smoke: grey skies you shouldn't breathe
From late summer into autumn, California's fire season can send smoke over the Bay from fires hundreds of miles away — no local flames required. The sky hazes over, sunsets turn lurid orange, and air quality can slide into genuinely unhealthy territory.
The catch is that smoke and fog can look similar from a sidewalk. That's where the air-quality layer earns its place: clean readings under a grey sky mean it's just the harmless marine layer; poor readings mean it's smoke, and time to close the windows. Tracking where that smoke comes from and how far it has travelled turns an eerie sky into something you can anticipate.
The rain: all at once, in winter
San Francisco's rain is famously seasonal — bone-dry summers, then a winter that arrives in concentrated pulses. Most of it comes from atmospheric rivers: long ribbons of Pacific moisture that can dump weeks of rain in a day or two and drive flooding and mudslides. The radar layer can sit quiet for months, then suddenly light up as one of these firehoses aims at the coast.
Reading the Bay Area sky on the live map
The trick in San Francisco is using the layers together to identify which kind of "grey" you're looking at:
- Smooth coastal cloud on satellite + clean air → marine-layer fog.
- Hazy sky + poor air-quality numbers → wildfire smoke.
- Bright, moving radar returns → real rain, usually a winter atmospheric river.
Pick San Francisco on the map and you'll drop straight onto the Bay with these layers ready to compare. Three iconic, totally different weather stories — and one map that finally lets you tell them apart at a glance.
Frequently asked questions
Why is San Francisco so foggy in summer?
It's a natural air-conditioning system. In summer the hot Central Valley inland draws in cool, moist air off the cold Pacific, and that cold ocean — kept chilly by upwelling — condenses the incoming air into the famous low fog that pours through the Golden Gate, especially in the afternoon and evening. On satellite it shows as a smooth grey sheet hugging the coast and spilling inland through the gaps, quite different from the textured cloud of a storm.
When is wildfire smoke worst in the Bay Area?
Typically late summer through autumn, when California's fire season peaks. Smoke from fires hundreds of miles away can drift over the Bay, turning skies orange and pushing air quality into unhealthy ranges even with no local fire. Because smoke and fog can look similar from the ground, the air-quality layer is the reliable way to tell whether that haze is harmless marine cloud or something you shouldn't be breathing.
Does it actually rain in San Francisco?
Yes, but it's highly seasonal. Summers are famously dry; the rain comes in winter, often delivered in concentrated bursts by atmospheric rivers streaming in off the Pacific. A strong one can drop weeks' worth of rain in a couple of days and drive flooding, so a quiet radar for months can suddenly light up with a firehose of moisture aimed straight at the coast.
How do I tell fog, smoke and rain apart on the map?
Use the layers together. Smooth grey cloud hugging the coast on satellite, with clean air-quality readings, is the marine-layer fog. Hazy skies with poor air-quality numbers point to wildfire smoke. Bright, moving returns on radar mean actual rain — usually a winter atmospheric river. Three very different things that can all make a 'grey' Bay Area sky, told apart by reading satellite, air quality and radar side by side.
SEE IT LIVE
Everything in this guide is on one real-time map.