September 20 sees frequent showers in San Juan. Historical data shows a 57% chance of rain, so pack accordingly. Temperatures average 31°C. You'll enjoy San Juan with reasonable crowd levels and competitive accommodation options.
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Essential Travel Info for San Juan
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Language
English
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Driving
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San Juan Weather Forecast for September 20
"Rainy & Overcast. Expect average highs of 30.7°C. 57% chance of rain."
What to Wear in San Juan in September
Based on historical data for September 20, San Juan typically experiences temperatures between 24.7°C and 30.7°C. We recommend packing t-shirt, light clothing, umbrella to stay comfortable. With a 57% chance of rain, keeping a raincoat or umbrella handy is a smart move.
Complete Packing Guide
Weekly breakdown & essential items for San Juan
Smart Suitcase
- T-Shirt
- Light Clothing
- Umbrella
Average High
30.7°C
Daytime Peak
Average Low
24.7°C
Nighttime Low
Feels Like
40.6°C
🔥 Heat index effect
Rain Chance
57%
Avg 3.9mm if it rains
Cloud Cover
66%
Light drizzle
Pressure
1012.7 hPa
Low volatility
San Juan Weather Conditions & UV Index
Weather Confidence
30-year variance analysis
Based on 10 years of data
🎯 This date historically delivers consistent weather 94% of the time. Safe to plan outdoor activities with confidence.
Sun Exposure
UV Index & Safety Guide
Protection Needed
SPF 30 recommended
06:00 - 10:00
16:00 - 18:00
Type I-II
🔴 26 min to burn
Type III-IV
🟡 39 min to burn
Type V-VI
🟢 65 min to burn
UV estimate based on latitude, season & cloud cover. Actual UV may vary.
Outdoor Comfort
How pleasant is it outside?
Dew Point
27.3°C
Humid/Sticky
Heat Index
40.6°C
Feels hotter
😕 Best outdoor time:
Early morning (6-9 AM) or evening (after 6 PM)
Marine Conditions
Jellyfish Warning
High water temps may attract jellyfish swarms.
Swim Index
⚠️ Mixed Conditions
Travel & Logistics Insights
Local Calendar
Business Day
Standard hours in Puerto Rico
Flight Traffic
Moderate
50/100 pressure index
Health Advisory
Required
2 vaccines • View Details →
Landing Slots
~109
Daily arrival options (inc. codeshare)
Sunrise, Sunset & Wind in San Juan
Daylight & Sun
Solar Elevation Cycle
🌅 Sunrise
06:14
☀️ Noon
12:19
🌇 Sunset
18:24
⏱️ Daylight
12h 9m
Wind Speed
17 km/h
Gentle breeze
Sunshine
9.9 hrs
Direct Sun (Cloud-free)
Humidity
82%
Humid / Damp
Travel Intelligence
Exclusive flight analytics & health data for San Juan
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 Juan
Travel Comfort Index
Real-time tourism conditions
Weather Quality
🌧️ Variable
Tourist Crowds
🟡 Busy
Price Level
💰💰💰 Expensive
Health & Wellbeing
Meteo-Health Forecast
Stable conditions. Low risk of headaches.
Mild discomfort possible for arthritic conditions.
Moderate fish activity expected.
Air quality is excellent. Perfect for outdoor activities.
Regional Safety Profile
Seismic Activity
Moderate seismic activity. Occasional tremors possible.
Atlantic Hurricane Risk
Season: Jun - Nov
"According to 30YearWeather's analysis of 30 years of NASA satellite data, San Juan on September 20 averages 30.7°C with a 57% precipitation probability. Wedding/Outdoor Event Score: 69/100."
— Source: 30YearWeather.com|Data: NASA POWER (1991-2021)|View Methodology
San Juan Weather History (2010–2024)
Temperature History
Hall of Fame
Records from last 10 years
Better Alternatives Nearby
Consider these dates within ±7 days
September 25
30.9°C • 41% rain
Score
79
September 14
31.1°C • 41% rain
Score
78
September 15
31.2°C • 42% rain
Score
78
💡 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 San Juan Worth Visiting on September 20?
Planning a trip to San Juan on September 20? Our historical weather analysis based on 30 years of NASA satellite data shows that this time of year typically offers vibrant summer conditions averaging 30.7°C with a 57% historical precipitation risk.
✈️ Travel Logistics: Approximately 109 landing slots available daily during this period, indicating manageable crowd levels.
💉 Health Advisory: 7 vaccinations are recommended for Puerto Rico, including COVID-19.
🌊 Coastal Conditions: Water temperature averages 30.2°C (hot soup). Wave conditions are generally surfers only with heights around 1.24m.
📊 Historical Extremes: The hottest September 20 recorded in the last 30 years saw temperatures hit 34.4°C in 2018, while the coldest dropped to 23.2°C in 2020.