Hottest (avg)
#1 / 12
The warmest month of the year.
September in context
How it compares to the rest of the year in Honolulu.
Wettest (avg)
#12 / 12
One of the drier months.
Daylight Hours
#6 / 12
Around the yearly average.
Windiest (avg)
#7 / 12
Close to the yearly wind average.
Highest UV
#6 / 12
Near the middle of the yearly UV range.
Most Humid
#8 / 12
Humidity stays close to the yearly norm.
Monthly climate breakdown
A detailed look at the typical climate conditions for September.
Thermal profile
Temperature
Typical daytime high
- Nighttime low
-
- Feels like (avg)
-
Light window
Sunshine
12.3 h
Average daylight
- UV index (max)
- 9
- Typical sun hours
- 06:18 - 18:33
Wet-day pattern
Rain & Snow
Typical rainfall
- Rainy days
- 13 days
- Cloud cover (avg)
- 41%
Air feel
Humidity & Wind
73%
Average humidity
- Wind (avg)
-
- Wind (max gusts)
-
Historical daily baseline
Daily climate explorer
Pick a day to inspect the usual conditions through September in Honolulu. Based on a 30-year historical climate baseline, not a forecast.
Primary control
Select a day
Scroll to compare daily conditions. The summary updates with your selection.
Secondary context
Monthly trend
Median daytime highs across the month, with a softer low line.
Median temperatureMedian lowTypical range
Day 15 selected for September. Temperature 28.2°C.
Historical disruption baseline
Typical disruptions in September
Based on 30 years of historical data, these are the disruption patterns most likely to affect plans in September.
Humidity High impact
Muggy days Measures: Muggy days (dew point >=20C). Observed about 66% of days (19.9 days/month) in September. Historical risk signal only, not a day-by-day forecast.
Likely frequency
19.9 days / month
- Share of days
- ~66% of days
- Upper edge
- Up to ~23°C (P95)
Why this matters
Muggy conditions are possible on ~20 days. Fixed-time outdoor plans are safer with a backup option and flexible timing.
Heat High impact
Hot feels-like days Measures: Hot feels-like days (>=32C). Observed about 27% of days (8.1 days/month) in September. Historical risk signal only, not a day-by-day forecast.
Likely frequency
8.1 days / month
- Share of days
- ~27% of days
- Upper edge
- Up to ~35°C (P95)
Why this matters
Feels-like heat >=32C is possible on ~8 days. Midday activity often needs adjustment around shade, hydration, and indoor fallback options.
Wind High impact
Strong gusts Measures: Strong gust days (>=60 km/h). Observed about 2% of days (0.7 days/month) in September. Historical risk signal only, not a day-by-day forecast.
Likely frequency
0.7 days / month
- Share of days
- ~2% of days
- Upper edge
- Up to ~70km/h (P95)
Why this matters
Strong gusts are possible on ~1 days. Exposed activities and transport links are more likely to be disrupted, so keep sheltered alternatives ready.
Heat High impact
Very hot feels-like Measures: Very hot feels-like days (>=35C). Observed about 2% of days (0.6 days/month) in September. Historical risk signal only, not a day-by-day forecast.
Likely frequency
0.6 days / month
- Share of days
- ~2% of days
- Upper edge
- Up to ~37°C (P95)
Why this matters
Very hot feels-like conditions are possible on ~1 days. Midday activity often needs adjustment around shade, hydration, and indoor fallback options.
Heat Moderate
Hot days Measures: Hot days (>=30C). Observed about 6% of days (1.8 days/month) in September. Historical risk signal only, not a day-by-day forecast.
Likely frequency
1.8 days / month
- Share of days
- ~6% of days
- Upper edge
- Up to ~31°C (P95)
Why this matters
Hot days are possible on ~2 days. Midday activity often needs adjustment around shade, hydration, and indoor fallback options.
Heat Moderate
Feels-like heatwave Measures: Feels-like heatwave runs (>=3 days). Observed about 1.1 days/month in September. Historical risk signal only, not a day-by-day forecast.
Likely frequency
1.1 days / month
- Share of days
- —
- Upper edge
- Up to ~35°C (P95)
Why this matters
Feels-like heatwave runs are possible on ~1 days. Midday activity often needs adjustment around shade, hydration, and indoor fallback options.
Show all disruptions (17 more)
Rain High impact
Washout risk Measures: Washout day risk. Observed about 1% of days (0.3 days/month) in September. Historical risk signal only, not a day-by-day forecast.
Likely frequency
0.3 days / month
- Share of days
- ~1% of days
- Upper edge
- Up to ~20mm (P95)
Why this matters
Washout conditions are possible on ~0 days. Outdoor plans can become unreliable, so keep an indoor backup and flexibility around start times.
Rain Moderate
Rain disruption Measures: Likely rain disruption days. Observed about 1% of days (0.3 days/month) in September. Historical risk signal only, not a day-by-day forecast.
Likely frequency
0.3 days / month
- Share of days
- ~1% of days
- Upper edge
- Up to ~20mm (P95)
Why this matters
Rain disruption risk appears on ~0 days. Outdoor plans can become unreliable, so keep an indoor backup and flexibility around start times.
Heat Minor
Warm nights Measures: Warm nights (min >=22C). Observed about 99% of days (29.8 days/month) in September. Historical risk signal only, not a day-by-day forecast.
Likely frequency
29.8 days / month
- Share of days
- ~99% of days
- Upper edge
- Up to ~26°C (P95)
Why this matters
Warm nights are possible on ~30 days. Fixed-time outdoor plans are safer with a backup option and flexible timing.
Humidity Minor
Humid days Measures: Humid days (dew point >=18C). Observed about 99% of days (29.8 days/month) in September. Historical risk signal only, not a day-by-day forecast.
Likely frequency
29.8 days / month
- Share of days
- ~99% of days
- Upper edge
- Up to ~23°C (P95)
Why this matters
Humid conditions are possible on ~30 days. Comfort and pace can drop quickly, so plan shorter outdoor blocks with air-conditioned backup stops.
Wind Minor
Gusty days Measures: Gusty days (>=40 km/h). Observed about 72% of days (21.7 days/month) in September. Historical risk signal only, not a day-by-day forecast.
Likely frequency
21.7 days / month
- Share of days
- ~72% of days
- Upper edge
- Up to ~59km/h (P95)
Why this matters
Gusty conditions are possible on ~22 days. Exposed activities and transport links are more likely to be disrupted, so keep sheltered alternatives ready.
Rain Minor
Wet days Measures: Wet days (>=0.1mm). Observed about 62% of days (18.6 days/month) in September. Historical risk signal only, not a day-by-day forecast.
Likely frequency
18.6 days / month
- Share of days
- ~62% of days
- Upper edge
- Up to ~2.9mm (P95)
Why this matters
Measurable rain is possible on ~19 days. Fixed-time outdoor plans are safer with a backup option and flexible timing.
Rain Minor
Rainy hours Measures: Rain-hours signal (>=3h rain). Observed about 44% of days (13.2 days/month) in September. Historical risk signal only, not a day-by-day forecast.
Likely frequency
13.2 days / month
- Share of days
- ~44% of days
- Upper edge
- Up to ~12h (P95)
Why this matters
Several rainy hours are possible on ~13 days. Outdoor plans can become unreliable, so keep an indoor backup and flexibility around start times.
Rain Minor
Wet most of day Measures: Wet-most-of-day signal (>=6h rain). Observed about 23% of days (6.8 days/month) in September. Historical risk signal only, not a day-by-day forecast.
Likely frequency
6.8 days / month
- Share of days
- ~23% of days
- Upper edge
- Up to ~14h (P95)
Why this matters
Wet-most-of-day conditions are possible on ~7 days. Outdoor plans can become unreliable, so keep an indoor backup and flexibility around start times.
Heat Minor
Hot nights Measures: Hot nights (min >=25C). Observed about 22% of days (6.6 days/month) in September. Historical risk signal only, not a day-by-day forecast.
Likely frequency
6.6 days / month
- Share of days
- ~22% of days
- Upper edge
- Up to ~26°C (P95)
Why this matters
Hot nights are possible on ~7 days. Midday activity often needs adjustment around shade, hydration, and indoor fallback options.
Cloud Minor
Cloudy days Measures: Cloudy days (cloud cover >=60%). Observed about 18% of days (5.3 days/month) in September. Historical risk signal only, not a day-by-day forecast.
Likely frequency
5.3 days / month
- Share of days
- ~18% of days
- Upper edge
- Up to ~96% (P95)
Why this matters
Cloudy skies are possible on ~5 days. Fixed-time outdoor plans are safer with a backup option and flexible timing.
Humidity Minor
High humidity Measures: High humidity days (RH >=80%). Observed about 7% of days (2.0 days/month) in September. Historical risk signal only, not a day-by-day forecast.
Likely frequency
2.0 days / month
- Share of days
- ~7% of days
- Upper edge
- Up to ~85% (P95)
Why this matters
High humidity is possible on ~2 days. Comfort and pace can drop quickly, so plan shorter outdoor blocks with air-conditioned backup stops.
Cloud Minor
Mostly cloudy days Measures: Mostly cloudy days (cloud cover >=80%). Observed about 6% of days (1.8 days/month) in September. Historical risk signal only, not a day-by-day forecast.
Likely frequency
1.8 days / month
- Share of days
- ~6% of days
- Upper edge
- Up to ~98% (P95)
Why this matters
Mostly cloudy skies are possible on ~2 days. Fixed-time outdoor plans are safer with a backup option and flexible timing.
Wind Minor
Breezy days Measures: Breezy days (mean wind >=25 km/h). Observed about 2% of days (0.7 days/month) in September. Historical risk signal only, not a day-by-day forecast.
Likely frequency
0.7 days / month
- Share of days
- ~2% of days
- Upper edge
- Up to ~30km/h (P95)
Why this matters
Breezy conditions are possible on ~1 days. Exposed activities and transport links are more likely to be disrupted, so keep sheltered alternatives ready.
Heat Minor
Heat stress risk Measures: High heat stress days. Observed about 2% of days (0.6 days/month) in September. Historical risk signal only, not a day-by-day forecast.
Likely frequency
0.6 days / month
- Share of days
- ~2% of days
- Upper edge
- Up to ~37°C (P95)
Why this matters
Heat stress is possible on ~1 days. Midday activity often needs adjustment around shade, hydration, and indoor fallback options.
Cloud Minor
Overcast days Measures: Overcast days (cloud cover >=95%). Observed about 1% of days (0.4 days/month) in September. Historical risk signal only, not a day-by-day forecast.
Likely frequency
0.4 days / month
- Share of days
- ~1% of days
- Upper edge
- Up to ~98% (P95)
Why this matters
Overcast skies are possible on ~0 days. Fixed-time outdoor plans are safer with a backup option and flexible timing.
Humidity Minor
Convective risk Measures: Convective storm risk proxy. Observed about 1% of days (0.3 days/month) in September. Historical risk signal only, not a day-by-day forecast.
Likely frequency
0.3 days / month
- Share of days
- ~1% of days
- Upper edge
- Up to ~24°C (P95)
Why this matters
Convective risk signal appears on ~0 days. Fixed-time outdoor plans are safer with a backup option and flexible timing.
Heat Minor
Heatwave run Measures: Heatwave runs (>=3 hot days). Observed about 0.1 days/month in September. Historical risk signal only, not a day-by-day forecast.
Likely frequency
0.1 days / month
- Share of days
- —
- Upper edge
- Up to ~31°C (P95)
Why this matters
Heatwave runs are possible on ~0 days. Midday activity often needs adjustment around shade, hydration, and indoor fallback options.
Travel planning FAQ
Frequently asked questions
Quick answers to the weather questions you ask the most.
Is September a good time to visit Honolulu?
Typical September days in Honolulu reach highs of 28°C (82°F) with nights around 24°C (75°F). It usually feels hot by day and warm after dark. It is one of the drier months, which suits outdoor exploring and sightseeing.
What are temperatures like in September?
In September, you can usually expect highs of 28°C (82°F) and lows near 24°C (75°F). That means hot days and warm nights, so pack layers you can add or remove.
How much does it rain in September?
Rainfall in September averages 20 mm (0.79 in) across roughly 13 days. Overall it is a quite rainy time of year, so a light rain jacket and waterproof shoes are very handy.
How many hours of daylight are there in September?
You can expect about 12 hours of daylight in September. Sunrise is typically around 06:18 and sunset near 18:33. Daylight is fairly typical, with enough time for sightseeing.
How strong is the sun in September?
UV levels frequently reach very high levels (around 9), so strong sun protection is essential, especially around midday.
Is it windy in September?
In September, average wind speeds are around 17 km/h (11 mph), with gusts on the windiest days reaching about 55 km/h (34 mph). On the ground, it is it can feel quite windy at times, particularly when weather systems move through.