San Francisco is located in a Mediterranean climate. The rainy season usually lasts from November to March; rainfall is unlikely from April through October.
The warmest months are usually September and October. The famous San Francisco fog begins rolling in through the Golden Gate in the spring and can persist throughout the summer months.
That said, the city can be foggy and windy any time of the year, so if your visit to “sunny California” includes a stop in San Francisco, bring some warm clothing.
The average annual temperature is 62.5°F (16.9°C). The Bay Area is known for its microclimates, which can change dramatically from neighborhood to neighborhood.