September 17 is statistically one of the best days of the year in San Francisco. With minimal rain risk (2%) and pleasant highs of 21°C, it's ideal for outdoor adventures. As it's peak season for San Francisco, we recommend booking your stay well in advance to secure the best rates.
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Essential Travel Info for San Francisco
Currency
USD
$ United States dollar
Language
English
Driving
Right side
Connect
Thearea codesfor San Francisco are 415 a...
Safety
Moderate Safety
GPI: 2.44
San Francisco Weather Forecast for September 17
"Mild & Comfortable. Expect average highs of 21.2°C. 2% chance of rain."
What to Wear in San Francisco in September
Based on historical data for September 17, San Francisco typically experiences temperatures between 13.7°C and 21.2°C. We recommend packing light jacket, long pants to stay comfortable. Trends suggest it will stay mostly dry (2% rain probability), but checking the forecast before heading out is always wise.
Complete Packing Guide
Weekly breakdown & essential items for San Francisco
Smart Suitcase
- Light Jacket
- Long Pants
Average High
21.2°C
Daytime Peak
Average Low
13.7°C
Nighttime Low
Feels Like
21.4°C
☀️ Feels accurate
Rain Chance
2%
Avg 0mm if it rains
Cloud Cover
37%
Overcast
Pressure
1013.3 hPa
Low volatility
San Francisco Weather Conditions & UV Index
Weather Confidence
30-year variance analysis
Based on 10 years of data
🎯 This date historically delivers consistent weather 99% of the time. Safe to plan outdoor activities with confidence.
Sun Exposure
UV Index & Safety Guide
Protection Needed
SPF 30 recommended
05:00 - 10:00
16:00 - 18:00
Type I-II
🔴 23 min to burn
Type III-IV
🟡 35 min to burn
Type V-VI
🟢 58 min to burn
UV estimate based on latitude, season & cloud cover. Actual UV may vary.
Outdoor Comfort
How pleasant is it outside?
Dew Point
17.2°C
Noticeable
Heat Stress
Low
No heat warning
🙂 Best outdoor time:
Any time during daylight hours
Marine Conditions
Marine Life
No special warnings. Enjoy the swim!
Swim Index
❄️ Cold Water Hazard
Travel & Logistics Insights
Local Calendar
Business Day
Standard hours in United States
Flight Traffic
High
94/100 pressure index
Health Advisory
Healthy
Routine only • View Details →
Landing Slots
~2,051
Daily arrival options (inc. codeshare)
Sunrise, Sunset & Wind in San Francisco
Daylight & Sun
Solar Elevation Cycle
🌅 Sunrise
05:54
☀️ Noon
12:05
🌇 Sunset
18:16
⏱️ Daylight
12h 22m
Wind Speed
21 km/h
Moderate wind
Sunshine
10.6 hrs
Direct Sun (Cloud-free)
Humidity
78%
Humid / Damp
Travel Intelligence
Exclusive flight analytics & health data for San Francisco
Smart Flight Estimator
Airport-to-Airport Logistics
unlock smart flight estimates
Add your home location in settings to see airport details.
Travel Health & Safety in San Francisco
Travel Comfort Index
Real-time tourism conditions
Weather Quality
☀️ Excellent
Tourist Crowds
🟡 Busy
Price Level
💰💰💰 Expensive
Health & Wellbeing
Meteo-Health Forecast
Stable conditions. Low risk of headaches.
Weather unlikely to affect joint pain.
Moderate fish activity expected.
Air quality is excellent. Perfect for outdoor activities.
Regional Safety Profile
Seismic Activity
Moderate seismic activity. Occasional tremors possible.
Eastern Pacific Hurricane Risk
Season: May - Nov
Travel Alert: This region has elevated natural risks. We recommend registering with your embassy and keeping emergency numbers handy.
"According to 30YearWeather's analysis of 30 years of NASA satellite data, San Francisco on September 17 averages 21.2°C with a 2% precipitation probability. Wedding/Outdoor Event Score: 100/100."
— Source: 30YearWeather.com|Data: NASA POWER (1991-2021)|View Methodology
San Francisco Weather History (2010–2024)
Temperature History
Hall of Fame
Records from last 10 years
Compare Other Cities
Same date (September 17) in other destinations
🌍 Explore the same date in different destinations around the world
📍 Is San Francisco Worth Visiting on September 17?
Planning a trip to San Francisco on September 17? Our historical weather analysis based on 30 years of NASA satellite data shows that this time of year is characterized by pleasant mild weather averaging 21.2°C with a 2% historical precipitation risk.
✈️ Travel Logistics: Approximately 2,051 landing slots available daily during this period, indicating peak tourist activity.
🌊 Coastal Conditions: Water temperature averages 16.4°C (polar plunge). Wave conditions are generally fun waves with heights around 1.12m.
📊 Historical Extremes: The hottest September 17 recorded in the last 30 years saw temperatures hit 24.2°C in 2016, while the coldest dropped to 11.7°C in 2016.