San Francisco has a Mediterranean climate, classified as Csb in the Köppen system. The warmest month is September with an average high of 23°C, while the coldest month is January with lows dropping to 7°C. The annual temperature range of 16°C reflects moderate seasonal variation.
The driest month is September with only 0 rain days and 2mm of precipitation. For travellers, September through to the following month typically offers the best balance of warm temperatures and dry conditions. Average humidity ranges from 65% to 65% throughout the year.
Best Time to Visit San Francisco
Based on temperature and rainfall data, the best months to visit San Francisco are April, May, June. These months offer the most comfortable temperatures with relatively low rainfall, ideal for sightseeing and outdoor activities.
Frequently Asked Questions: San Francisco in September
In September, San Francisco experiences average highs of 23°C (73°F) and lows of 13°C (55°F). Expect around 0 rainy days and 12 hours of sunshine per day, with humidity averaging 65%. The 10°C gap between daytime and overnight temperatures is worth planning around: light layers work for most visitors during the day, but an overshirt or cardigan handles the cooler evenings. UV index averages 6, so sun protection is advisable on clear days.
San Francisco typically sees 0 rainy days in September, with total precipitation of around 2mm. This makes September one of the drier months of the year, and a reliable window for outdoor sightseeing and day trips. Rain showers tend to be brief when they do occur. For context, the driest month in San Francisco typically sees 4-6 fewer rain days than September.
Pack light layers, a light jacket for evenings, comfortable walking shoes, and sunscreen for San Francisco in September. Daytime temperatures of 23°C are pleasant, but the evening drop to 13°C means a jacket is essential if you plan to be out after dark. Rain is infrequent with only 0 wet days, so a light rain layer is optional. Comfortable walking shoes are a priority given the amount of ground most visitors cover.
Yes, September is an excellent time to visit San Francisco. With 12 daily sunshine hours and only 0 rainy days, conditions are ideal for sightseeing and outdoor activities. Temperatures averaging 23°C during the day are comfortable for long walks and outdoor dining. This is peak travel season, so booking accommodation in advance and arriving at popular attractions early in the morning helps avoid the busiest periods.
The average high temperature in San Francisco in September is 23°C (73°F), and the average low is 13°C (55°F). The mean daily temperature is approximately 18°C (64°F). The day-to-night range of 10°C is moderate, meaning a single light jacket covers most situations. These are 30-year climate normals based on the 1991 to 2020 reference period; individual years will vary, particularly in transitional months like spring and autumn.
The best month to visit San Francisco is generally July. July offers the most sunshine at 14 hours per day and only 0 rainy days. Average temperatures reach 21°C, making it comfortable for sightseeing, outdoor dining, and exploring the city. If your travel dates are flexible, planning your trip around July gives you the best chance of dry, bright weather.
September is shoulder or low season in San Francisco, meaning fewer tourists and generally lower prices than peak months. With 12 sunshine hours and 0 rainy days, the weather is less of a draw for mass tourism. This is an advantage for travellers who prefer a quieter, more relaxed experience with shorter queues and easier accommodation availability.
In September, San Francisco suits a range of activities thanks to mild temperatures around 23°C. With few rainy days, outdoor activities are highly recommended. Top options include exploring historic neighbourhoods, visiting museums and galleries, local food markets, and day trips to surrounding areas. With 12 hours of sunshine, parks and waterfront walks are particularly enjoyable.