San Francisco Weather in September
United States · Mediterranean climate · Data averaged from 2020-01-01 to 2024-12-31 (5 years)
September in San Francisco sees average temperatures ranging from a low of 14.4°C (57.9°F) to a high of 20.4°C (68.7°F), with a mean of 16.8°C (62.2°F). Compared to the annual average of 13.5°C (56.3°F), this month is 3.3°C warmer than the yearly norm. This is the hottest month of the year, reaching 20.4°C (68.7°F) on average. Precipitation averages 3.8mm, making it approximately 45.0mm drier than the monthly average of 49.0mm. The city receives an average of 11.3 hours of sunshine per day during September, with relative humidity averaging 80.2%. Wind speeds reach an average maximum of 27.4 km/h. For travelers, this month offers a hottest month of the year experience in San Francisco, with drier-than-average conditions compared to the rest of the year.
If you're planning outdoor activities in San Francisco, ignore the season — focus on the hour. I hiked Lands End in July at 2pm in a t-shirt and was shivering by 4pm when the fog rolled in. The 5°C temperature swing between coast and bay is real. Best running conditions: September-October, when the marine layer retreats and 22°C hits the city. Pack a windbreaker for any coastal trail, year-round. Marin Headlands is magnificent but windy; aim for 10am-2pm. February-March brings surprisingly green hills and empty trails — my favorite hiking window.
September vs Adjacent Months
| Metric | August | September | October |
|---|---|---|---|
| Mean Temp | 16.6°C (61.9°F) | 16.8°C (62.2°F) | 16.2°C (61.2°F) |
| Rainfall | 0.7mm | 3.8mm | 35.4mm |
| Sunshine | 12.2 hrs | 11.3 hrs | 9.6 hrs |
| Humidity | 81.0% | 80.2% | 74.5% |
| Wind | 29.6 km/h | 27.4 km/h | 24.5 km/h |
| Rainy Days | 1.4 | 2.8 | 4.4 |
Seasonal Context
September falls in Autumn in the Northern Hemisphere. Autumn sees temperatures gradually cooling from summer highs. For travelers visiting San Francisco in September, the data indicates favorable conditions based on the combination of temperature, precipitation, and daylight hours.
Frequently Asked Questions
What is the average temperature in San Francisco in September?
The average temperature in San Francisco during September ranges from 14.4°C (57.9°F) to 20.4°C (68.7°F), with a mean of 16.8°C (62.2°F).
How much does it rain in San Francisco in September?
San Francisco receives an average of 3.8mm of precipitation in September, spread across approximately 2.8 rainy days.
What should I pack for San Francisco in September?
Based on September weather data, pack layers including light jackets and t-shirts, plus an umbrella.
Is September a good time to visit San Francisco?
September is a good time to visit San Francisco, with comfortable temperatures and manageable rainfall. However, it is the hottest month — consider early morning or evening activities.
Other Months for San Francisco
Cities with Similar September Climate (Mediterranean)
Data Source: Open-Meteo historical archive (2020-01-01 to 2024-12-31). Daily measurements aggregated into monthly climate normals. Coordinates: 37.77°, -122.42°. Timezone: America/Los_Angeles. Last updated: 2026-07-30.