September 21 is statistically one of the best days of the year in Honolulu. With minimal rain risk (9%) and pleasant highs of 29°C, it's ideal for outdoor adventures. It's a lively time to explore Honolulu, with most attractions operating at full capacity.
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Essential Travel Info for Honolulu
Currency
USD
$ United States dollar
Language
English
Driving
Right side
Connect
The area code for Honolulu, and the rest...
Safety
Moderate Safety
GPI: 2.44
Honolulu Weather Forecast for September 21
"Warm & Sunny. Expect average highs of 28.6°C. 9% chance of rain."
What to Wear in Honolulu in September
Based on historical data for September 21, Honolulu typically experiences temperatures between 24.3°C and 28.6°C. We recommend packing t-shirt, light clothing to stay comfortable. Trends suggest it will stay mostly dry (9% rain probability), but checking the forecast before heading out is always wise.
Complete Packing Guide
Weekly breakdown & essential items for Honolulu
Smart Suitcase
- T-Shirt
- Light Clothing
Average High
28.6°C
Daytime Peak
Average Low
24.3°C
Nighttime Low
Feels Like
32.2°C
🔥 Feels warmer
Rain Chance
9%
Avg 0.5mm if it rains
Cloud Cover
41%
Light drizzle
Pressure
1015.6 hPa
Low volatility
Honolulu Weather Conditions & UV Index
Weather Confidence
30-year variance analysis
Based on 10 years of data
✓ This date historically delivers consistent weather 75% 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
🔴 20 min to burn
Type III-IV
🟡 30 min to burn
Type V-VI
🟢 50 min to burn
UV estimate based on latitude, season & cloud cover. Actual UV may vary.
Outdoor Comfort
How pleasant is it outside?
Dew Point
23°C
Humid/Sticky
Heat Index
32.2°C
Feels hotter
😐 Best outdoor time:
Morning hours (before 11 AM)
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 United States
Flight Traffic
Busy
71/100 pressure index
Health Advisory
Healthy
Routine only • View Details →
Landing Slots
~217
Daily arrival options (inc. codeshare)
Sunrise, Sunset & Wind in Honolulu
Daylight & Sun
Solar Elevation Cycle
🌅 Sunrise
06:21
☀️ Noon
12:25
🌇 Sunset
18:30
⏱️ Daylight
12h 9m
Wind Speed
22.3 km/h
Moderate wind
Sunshine
11.0 hrs
Direct Sun (Cloud-free)
Humidity
72%
Humid / Damp
Travel Intelligence
Exclusive flight analytics & health data for Honolulu
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 Honolulu
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
Rare minor tremors. Buildings are earthquake-resistant.
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, Honolulu on September 21 averages 28.6°C with a 9% precipitation probability. Wedding/Outdoor Event Score: 100/100."
— Source: 30YearWeather.com|Data: NASA POWER (1991-2021)|View Methodology
Honolulu Weather History (2010–2024)
Temperature History
Hall of Fame
Records from last 10 years
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📍 Is Honolulu Worth Visiting on September 21?
Planning a trip to Honolulu on September 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 28.6°C with a 9% historical precipitation risk.
✈️ Travel Logistics: Approximately 217 landing slots available daily during this period, indicating manageable crowd levels.
🌊 Coastal Conditions: Water temperature averages 26.9°C (tropical bath). Wave conditions are generally surfers only with heights around 1.2m.
📊 Historical Extremes: The hottest September 21 recorded in the last 30 years saw temperatures hit 29.8°C in 2019, while the coldest dropped to 22.5°C in 2024.