September is often the warmest month of the year, along with October. Fog thins out, skies are clearer and the average high is about 70°F. Rain is rare.
In this guide
This guide is part of our San Francisco weather by month hub. For trip planning, see the San Francisco visitors guide.
September averages, San Francisco Downtown
- Average high 70°F
- Average low 56°F
- Average rainfall 0.1 inch
- Rainy days 0 (days with at least 0.1 inch)
- Source NOAA 1991 to 2020 climate normals
What the weather is like
Heat waves can push temperatures into the 80s or higher for a few days. Ocean Beach and the Presidio are more likely to be clear than in summer, and evenings are milder.
These averages come from the downtown station. Neighborhoods near Ocean Beach are often cooler and grayer, and the Mission and SoMa are often warmer. In September the station records almost no days with measurable rain in an average year.
What to pack
Pack lighter clothing but still bring a sweater or light jacket for the evening, when it cools down fast. Our San Francisco packing list covers the basics for every season.
What is on in September
Fall street fairs and outdoor concerts pick up in September as the weather warms. See San Francisco events in September for dates and details.
Planning around the weather
Compare September with the months either side: August and October. If you are still choosing dates, read the best time to visit San Francisco.
Official resources: NOAA U.S. climate normals, National Weather Service Bay Area forecast.
Frequently asked questions
How warm is San Francisco in September?
The average high at the downtown station is 70°F and the average low is 56°F.
Is September the warmest month in San Francisco?
September and October have the highest average highs, about 70°F at the downtown station.
Photo credits
Featured image: Radomianin / Wikimedia Commons, CC BY-SA 4.0.