September 20 is generally a great time to visit Siena. While there is a slight chance of rain (28%), showers are usually brief. Expect comfortable 24°C weather. Siena is currently in its most popular travel window, meaning vibrant crowds and premium pricing.
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Essential Travel Info for Siena
Currency
EUR
€ Euro
Language
Italian
+1 more
Driving
Right side
Safety
High Safety
GPI: 1.643
Siena Weather Forecast for September 20
"Mild & Comfortable. Expect average highs of 23.7°C. 28% chance of rain."
What to Wear in Siena in September
Based on historical data for September 20, Siena typically experiences temperatures between 13.7°C and 23.7°C. We recommend packing t-shirt, light clothing to stay comfortable. With a 28% chance of rain, keeping a raincoat or umbrella handy is a smart move.
Complete Packing Guide
Weekly breakdown & essential items for Siena
Smart Suitcase
- T-Shirt
- Light Clothing
Average High
23.7°C
Daytime Peak
Average Low
13.7°C
Nighttime Low
Feels Like
24.3°C
☀️ Feels accurate
Rain Chance
28%
Avg 2.2mm if it rains
Cloud Cover
50%
Overcast
Pressure
1016 hPa
Medium volatility
Siena Weather Conditions & UV Index
Weather Confidence
30-year variance analysis
Based on 10 years of data
🎯 This date historically delivers consistent weather 95% of the time. Safe to plan outdoor activities with confidence.
Sun Exposure
UV Index & Safety Guide
Protection Needed
SPF 15 for extended outdoor time
Type I-II
🔴 28 min to burn
Type III-IV
🟡 42 min to burn
Type V-VI
🟢 70 min to burn
UV estimate based on latitude, season & cloud cover. Actual UV may vary.
Outdoor Comfort
How pleasant is it outside?
Dew Point
18.6°C
Noticeable
Heat Stress
Low
No heat warning
😊 Best outdoor time:
Any time during daylight hours
Travel & Logistics Insights
Local Calendar
Business Day
Standard hours in Italy
Flight Traffic
High
95/100 pressure index
Health Advisory
Required
1 vaccine • View Details →
Landing Slots
~61
Daily arrival options (inc. codeshare)
Sunrise, Sunset & Wind in Siena
Daylight & Sun
Solar Elevation Cycle
🌅 Sunrise
06:00
☀️ Noon
12:09
🌇 Sunset
18:18
⏱️ Daylight
12h 17m
Wind Speed
12.5 km/h
Gentle breeze
Sunshine
9.6 hrs
Direct Sun (Cloud-free)
Humidity
73%
Humid / Damp
Travel Intelligence
Exclusive flight analytics & health data for Siena
Smart Flight Estimator
Airport-to-Airport Logistics
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Travel Health & Safety in Siena
Travel Comfort Index
Real-time tourism conditions
Weather Quality
⛅ Good
Tourist Crowds
🟡 Busy
Price Level
💰💰💰 Expensive
Health & Wellbeing
Meteo-Health Forecast
Moderate fluctuations. Some sensitivity possible.
Weather unlikely to affect joint pain.
Moderate fish activity expected.
Air quality is acceptable. Sensitive individuals should limit prolonged outdoor exertion.
Regional Safety Profile
Seismic Activity
Moderate seismic activity. Occasional tremors possible.
"According to 30YearWeather's analysis of 30 years of NASA satellite data, Siena on September 20 averages 23.7°C with a 28% precipitation probability. Wedding/Outdoor Event Score: 96/100."
— Source: 30YearWeather.com|Data: NASA POWER (1991-2021)|View Methodology
Siena Weather History (2010–2024)
Temperature History
Hall of Fame
Records from last 10 years
Better Alternatives Nearby
Consider these dates within ±7 days
September 13
25.8°C • 20% rain
Score
98
September 27
21.9°C • 20% rain
Score
98
September 14
25.4°C • 24% rain
Score
97
💡 Moving your event by a few days could significantly improve weather conditions
Compare Other Cities
Same date (September 20) in other destinations
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🌍 Explore the same date in different destinations around the world
📍 Is Siena Worth Visiting on September 20?
Planning a trip to Siena on September 20? 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 23.7°C with a 28% historical precipitation risk.
✈️ Travel Logistics: Approximately 61 landing slots available daily during this period, indicating manageable crowd levels.
💉 Health Advisory: 7 vaccinations are recommended for Italy, including COVID-19.
📊 Historical Extremes: The hottest September 20 recorded in the last 30 years saw temperatures hit 29.6°C in 2025, while the coldest dropped to 9.6°C in 2017.