San Francisco is famous for its mild climate, often associated with persistent fog and cool summers. While the question of whether it ever snows remains common, the definitive answer is yes, but the event is an extraordinary rarity. The city’s unique geography and prevailing weather patterns create a climate that is almost always too warm for precipitation to freeze and stick to the ground, meaning any snowfall is typically non-accumulating at sea level.
Historical Record of Snowfall in SF
Measurable snowfall in San Francisco has been documented only a handful of times since record-keeping began in the mid-19th century. The most significant event occurred on February 5, 1887, when the city received its heaviest snowfall on record, measuring 3.7 inches in the downtown area. This historic storm saw up to seven inches of accumulation in the city’s higher western reaches.
Other memorable instances include December 31, 1882, which saw 3.5 inches of snow, and the most recent accumulation on February 5, 1976. The 1976 event left about one inch of snow at sea level and up to five inches on Twin Peaks, covering the Golden Gate Bridge and Marin Headlands. While flurries have been reported since then, true measurable accumulation is extremely infrequent and melts quickly due to mild surface temperatures.
Why San Francisco Rarely Sees Snow
The primary reason for the lack of snow is the powerful moderating effect of the Pacific Ocean, specifically the cold California Current. This massive body of water acts like a giant thermostat, keeping winter temperatures on the coast reliably above freezing. Prevailing westerly winds continuously draw air off the ocean, which is too warm to allow precipitation to fall as snow at sea level.
For snow to fall and accumulate, two conditions must align: temperatures must drop to near or below 32 degrees Fahrenheit, and sufficient moisture must be present. San Francisco’s climate rarely allows for this simultaneous combination. Cold air masses moving south from the Gulf of Alaska lose their frigid temperatures as they pass over the warmer Pacific waters before reaching the city. Even when cold air penetrates the region, the moisture content is often too low, or the surface air remains just warm enough to turn the snow into rain before it reaches the ground.
Snow in the Surrounding Bay Area
While San Francisco remains largely snow-free, the broader Bay Area frequently sees snow at higher elevations. This difference is due to the rapid change in altitude found just a few miles outside the city limits. The snow line, the elevation above which snow begins to fall, typically sits between 1,000 and 3,000 feet during cold winter storms.
Local peaks often receive a visible dusting of snow. These include Mount Tamalpais (2,571 feet) in Marin County and Mount Diablo (3,849 feet) in the East Bay. Further south, Mount Hamilton, home to the Lick Observatory, also sees regular snowfall due to its elevation of 4,265 feet.