April 21 is generally a great time to visit San Juan. While there is a slight chance of rain (27%), showers are usually brief. Expect comfortable 30°C weather. As it's peak season for San Juan, we recommend booking your stay well in advance to secure the best rates. Note: April 21 is Birthday of José de Diego in San Juan, so expect special events, closures, and festive atmosphere.
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Essential Travel Info for San Juan
Currency
USD
$ United States dollar
Language
English
+1 more
Driving
Right side
San Juan Weather Forecast for April 21
"Warm & Sunny. Expect average highs of 29.6°C. 27% chance of rain."
What to Wear in San Juan in April
Based on historical data for April 21, San Juan typically experiences temperatures between 22.7°C and 29.6°C. We recommend packing t-shirt, light clothing to stay comfortable. With a 27% 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
Average High
29.6°C
Daytime Peak
Average Low
22.7°C
Nighttime Low
Feels Like
35.2°C
🔥 Heat index effect
Rain Chance
27%
Avg 2.3mm if it rains
Cloud Cover
50%
Light drizzle
Pressure
1015 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 82% 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
🔴 14 min to burn
Type III-IV
🟡 21 min to burn
Type V-VI
🟢 35 min to burn
UV estimate based on latitude, season & cloud cover. Actual UV may vary.
Outdoor Comfort
How pleasant is it outside?
Dew Point
24.7°C
Humid/Sticky
Heat Index
35.2°C
Feels hotter
😕 Best outdoor time:
Morning hours (before 11 AM)
Marine Conditions
Marine Life
No special warnings. Enjoy the swim!
Swim Index
⚠️ Mixed Conditions
Travel & Logistics Insights
Local Calendar
Holiday
Birthday of José de Diego
Flight Traffic
High
88/100 pressure index
Health Advisory
Required
2 vaccines • View Details →
Landing Slots
~190
Daily arrival options (inc. codeshare)
Sunrise, Sunset & Wind in San Juan
Daylight & Sun
Solar Elevation Cycle
🌅 Sunrise
06:04
☀️ Noon
12:24
🌇 Sunset
18:43
⏱️ Daylight
12h 39m
Wind Speed
19.1 km/h
Gentle breeze
Sunshine
11.3 hrs
Direct Sun (Cloud-free)
Humidity
75%
Humid / Damp
Travel Intelligence
Exclusive flight analytics & health data for San Juan
Smart Flight Estimator
Airport-to-Airport Logistics
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Travel Health & Safety in San Juan
Travel Comfort Index
Real-time tourism conditions
Weather Quality
⛅ Good
Tourist Crowds
🟡 Busy
Price Level
💰💰 Moderate
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.
Atlantic Hurricane Risk
Season: Jun - Nov
"According to 30YearWeather's analysis of 30 years of NASA satellite data, San Juan on April 21 averages 29.6°C with a 27% precipitation probability. Wedding/Outdoor Event Score: 91/100."
— 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
April 14
29.5°C • 20% rain
Score
95
April 16
29.5°C • 20% rain
Score
95
April 15
29.5°C • 22% rain
Score
94
💡 Moving your event by a few days could significantly improve weather conditions
Compare Other Cities
Same date (April 21) in other destinations
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📍 Is San Juan Worth Visiting on April 21?
Planning a trip to San Juan on April 21? Our historical weather analysis based on 30 years of NASA satellite data shows that this time of year typically offers vibrant summer conditions averaging 29.6°C with a 27% historical precipitation risk.
🎉 Local Event: The date coincides with Birthday of José de Diego, which may influence local business hours and event availability.
✈️ Travel Logistics: Approximately 190 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 27.2°C (tropical bath). Wave conditions are generally surfers only with heights around 1.29m.
📊 Historical Extremes: The hottest April 21 recorded in the last 30 years saw temperatures hit 32.5°C in 2020, while the coldest dropped to 21.3°C in 2023.