"The coldest winter I ever spent was a summer in San Francisco." This astute statement has often been attributed to legendary American storyteller Mark Twain, with his characteristic hyperbole.
Whoever first said it, he or she knew from whence they spoke.
San Francisco’s climate is, if nothing else, dependably changeable. Temperatures and conditions change literally by the hour and can differ markedly from one part of the city to the other.
Yet overall, the City by the Bay enjoys an eternally spring-like climate. Temperatures beside the Golden Gate average 54-65 degrees Fahrenheit (12-18 Celsius) in summer, 48-59 degrees (8-14 C) in winter. San Francisco residents save on wardrobe costs because the same clothes suffice year round — knits, light wools, long sleeves and pants.
In June, July and August, days usually start in fog, catching many vacationers off guard. Sweatshirts replace tee shirts as the souvenir of choice in popular tourist areas like Fisherman’s Wharf.
By noon the city is basking in bright sunlight. The fog returns just in time to put on a show during the cocktail and dinner hours as it curls over the tops of landmarks like the Golden Gate Bridge, Coit Tower and the Transamerica Pyramid. No extra charge for the entertainment.
Fall is the warmest season. The days of Indian Summer are in the upper 60’s F (15 C). The occasional arrival of 80 F (26 C) temperatures draws residents from their homes to bask at the City’s many parks and beaches.
Rainfall in San Francisco averages 19.33 inches per year, falling mostly in the late fall and early winter. Rains can be gentle or robust but with temperatures in such a moderate range, the experience is more refreshing than regrettable.
San Francisco’s automatic air conditioning is created by a unique combination of waters, winds and topography. During much of the summer a great fog bank hugs the cold currents off the Northern California coast. In the Central Valley the temperatures regularly reach 100 F (37 C) or more. The warmer temperatures inland draw the moisture-laden cool air eastward from the ocean. As the air warms, the fog evaporates.
There’s an apt, if oversimplified, adage that says the temperature goes up 10 degrees every 10 miles (160 km) you travel east from the city. When it’s a comfortable 65 F (18 C) in San Francisco, it will be 80 F (26 C) across the Golden Gate in Marin County to the north, on the Peninsula to the south, and in Contra Costa County to the east. Sacramento, 88 miles (141 km) away, Solano County, 45 miles (72 km) away, and the valley farmlands simmer in 90-100 F (31-37 C).
Morning mists notwithstanding, residents reach for their cottons and polyesters, shorts and chinos on weekends. You’ll see them sunning on the decks of waterfront restaurants in Sausalito and Tiburon, 25 minutes from the city by ferryboat; around the beaches, picnic sites and hiking/biking paths of Angel Island, Mount Tamalpais and the Marin headlands, and in the wine country a few miles farther north.
As the San Francisco Travel Association points out in its visitor guide “Visitors are most comfortable with a light jacket or coat handy, or in a suit. An all-weather coat will chill off cool evenings. Lightweight summer clothes are seldom practical in San Francisco.” Comfortable walking shoes are also a wise fashion choice.