What's the weather like in San Francisco in September?Sitting on the east coast of the United States in the state of California, San Francisco’s weather’s fairly mild all year round. Things are cooling down in September after the peak of summer but there’s still hardly any rain. You'll get a good amount of sun but evenings can be a bit chilly. San Francisco can often be foggy, which happens most over summer, and the west of the city gets the most fog because it’s closest to the sea. High hills in the city mean there’s more rain in certain areas, while you'll generally be warmer on the bay side of the city compared to the ocean side. San Francisco’s surrounded by lots of water which is why it’s cooler than other cities on the Californian coast.
AveragesThe average high in September is 22ºC, which cools to 13ºC at night. The sea temperature’s 14ºC, while humidity’s low. There’s 7mm of rain over two days, and you can expect 12 hours of daylight with nine hours of sunshine each day. UV levels will be high so don't forget your sun cream. Sunset’s around 7.40pm at the start of the month.