September 21 is generally a great time to visit Rotterdam. While there is a slight chance of rain (17%), showers are usually brief. Expect comfortable 19°C weather. As it's peak season for Rotterdam, we recommend booking your stay well in advance to secure the best rates.
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Essential Travel Info for Rotterdam
Currency
EUR
€ Euro
Language
Dutch
Driving
Right side
Connect
The telephone country code for the Nethe...
Safety
High Safety
GPI: 1.522
Rotterdam Weather Forecast for September 21
"Mild & Comfortable. Expect average highs of 18.7°C. 17% chance of rain."
What to Wear in Rotterdam in September
Based on historical data for September 21, Rotterdam typically experiences temperatures between 11.5°C and 18.7°C. We recommend packing light jacket, long pants to stay comfortable. Trends suggest it will stay mostly dry (17% rain probability), but checking the forecast before heading out is always wise.
Complete Packing Guide
Weekly breakdown & essential items for Rotterdam
Smart Suitcase
- Light Jacket
- Long Pants
Average High
18.7°C
Daytime Peak
Average Low
11.5°C
Nighttime Low
Feels Like
18.7°C
🌤️ Feels accurate
Rain Chance
17%
Avg 0.8mm if it rains
Cloud Cover
59%
Overcast
Pressure
1017.3 hPa
Medium volatility
Rotterdam 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 15 for extended outdoor time
Type I-II
🔴 36 min to burn
Type III-IV
🟡 54 min to burn
Type V-VI
🟢 90 min to burn
UV estimate based on latitude, season & cloud cover. Actual UV may vary.
Outdoor Comfort
How pleasant is it outside?
Dew Point
14.8°C
Pleasant
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
⚠️ Mixed Conditions
Travel & Logistics Insights
Local Calendar
Business Day
Standard hours in Netherlands
Flight Traffic
High
95/100 pressure index
Health Advisory
Required
1 vaccine • View Details →
Landing Slots
~35
Daily arrival options (inc. codeshare)
Sunrise, Sunset & Wind in Rotterdam
Daylight & Sun
Solar Elevation Cycle
🌅 Sunrise
06:27
☀️ Noon
12:36
🌇 Sunset
18:45
⏱️ Daylight
12h 18m
Wind Speed
18 km/h
Gentle breeze
Sunshine
8.7 hrs
Direct Sun (Cloud-free)
Humidity
78%
Humid / Damp
Travel Intelligence
Exclusive flight analytics & health data for Rotterdam
Smart Flight Estimator
Airport-to-Airport Logistics
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Add your home location in settings to see airport details.
Travel Health & Safety in Rotterdam
Travel Comfort Index
Real-time tourism conditions
Weather Quality
☀️ Excellent
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 excellent. Perfect for outdoor activities.
Regional Safety Profile
Seismic Activity
Rare minor tremors. Buildings are earthquake-resistant.
"According to 30YearWeather's analysis of 30 years of NASA satellite data, Rotterdam on September 21 averages 18.7°C with a 17% precipitation probability. Wedding/Outdoor Event Score: 95/100."
— Source: 30YearWeather.com|Data: NASA POWER (1991-2021)|View Methodology
Rotterdam Weather History (2010–2024)
Temperature History
Hall of Fame
Records from last 10 years
Compare Other Cities
Same date (September 21) in other destinations
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📍 Is Rotterdam Worth Visiting on September 21?
Planning a trip to Rotterdam on September 21? 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 18.7°C with a 17% historical precipitation risk.
✈️ Travel Logistics: Approximately 35 landing slots available daily during this period, indicating manageable crowd levels.
💉 Health Advisory: 7 vaccinations are recommended for Netherlands, including COVID-19.
🌊 Coastal Conditions: Water temperature averages 18.2°C (refreshing tonic). Wave conditions are generally lake-like with heights around 0m.
📊 Historical Extremes: The hottest September 21 recorded in the last 30 years saw temperatures hit 23.3°C in 2019, while the coldest dropped to 6.8°C in 2021.