Avg High
Hanoi in September
Avg Low
Rain
Daylight
12h
What to expect
September in Hanoi is early autumn, a shoulder-season window, so you can get a bit of variety across the month. It can feel distinctly hot through the middle of the day, with a noticeable cool-down after sunset. The daylight window is balanced for full days without endless late evenings. Most days feel close to what the averages suggest, with straightforward pacing.
September in context
How it compares to the rest of the year in Hanoi.
Hottest (avg)
#5 / 12
Wettest (avg)
#3 / 12
Daylight Hours
#6 / 12
Windiest (avg)
#11 / 12
Highest UV
#6 / 12
Most Humid
#2 / 12
Monthly climate breakdown
Temperature
- Daytime high
-
- Nighttime low
-
- Feels like (avg)
-
Sunshine
- Daylight hours
- 12.3 h
- UV index (max)
- 9
- Typical sun hours
- 05:43 - 17:59
Rain & Snow
- Total rain
-
- Rainy days
- 21 days
- Cloud cover (avg)
- 72%
Humidity & Wind
- Humidity (avg)
- 84%
- Wind (avg)
-
- Wind (max gusts)
-
Daily climate explorer
Day 15 selected for September. Typical high 30.7°C and low 24.4°C.
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 94% of days (28.3 days/month) in September. Historical risk signal only, not a day-by-day forecast.
28.3 days / month
~94% of days
Why this matters
- Expected days 28.3 days / month
- Probability ~94% of days
- Intensity Up to ~26°C (P95)
Muggy conditions are possible on ~28 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 90% of days (27.0 days/month) in September. Historical risk signal only, not a day-by-day forecast.
27.0 days / month
~90% of days
Why this matters
- Expected days 27.0 days / month
- Probability ~90% of days
- Intensity Up to ~41°C (P95)
Feels-like heat >=32C is possible on ~27 days. Midday activity often needs adjustment around shade, hydration, and indoor fallback options.
Heat High impact
Very hot feels-like Measures: Very hot feels-like days (>=35C). Observed about 65% of days (19.5 days/month) in September. Historical risk signal only, not a day-by-day forecast.
19.5 days / month
~65% of days
Why this matters
- Expected days 19.5 days / month
- Probability ~65% of days
- Intensity Up to ~41°C (P95)
Very hot feels-like conditions are possible on ~20 days. Midday activity often needs adjustment around shade, hydration, and indoor fallback options.
Heat High impact
Heat stress risk Measures: High heat stress days. Observed about 65% of days (19.5 days/month) in September. Historical risk signal only, not a day-by-day forecast.
19.5 days / month
~65% of days
Why this matters
- Expected days 19.5 days / month
- Probability ~65% of days
- Intensity Up to ~41°C (P95)
Heat stress is possible on ~20 days. Midday activity often needs adjustment around shade, hydration, and indoor fallback options.
Heat High impact
Hot days Measures: Hot days (>=30C). Observed about 64% of days (19.2 days/month) in September. Historical risk signal only, not a day-by-day forecast.
19.2 days / month
~64% of days
Why this matters
- Expected days 19.2 days / month
- Probability ~64% of days
- Intensity Up to ~34°C (P95)
Hot days are possible on ~19 days. Midday activity often needs adjustment around shade, hydration, and indoor fallback options.
Humidity High impact
Oppressive humidity Measures: Oppressive humidity days (dew point >=24C). Observed about 59% of days (17.6 days/month) in September. Historical risk signal only, not a day-by-day forecast.
17.6 days / month
~59% of days
Why this matters
- Expected days 17.6 days / month
- Probability ~59% of days
- Intensity Up to ~26°C (P95)
Oppressive humidity is possible on ~18 days. Fixed-time outdoor plans are safer with a backup option and flexible timing.
Show all disruptions (24 more)
Rain High impact
Rain disruption Measures: Likely rain disruption days. Observed about 44% of days (13.1 days/month) in September. Historical risk signal only, not a day-by-day forecast.
13.1 days / month
~44% of days
Why this matters
- Expected days 13.1 days / month
- Probability ~44% of days
- Intensity Up to ~50mm (P95)
Rain disruption risk appears on ~13 days. Outdoor plans can become unreliable, so keep an indoor backup and flexibility around start times.
Rain High impact
Washout risk Measures: Washout day risk. Observed about 42% of days (12.7 days/month) in September. Historical risk signal only, not a day-by-day forecast.
12.7 days / month
~42% of days
Why this matters
- Expected days 12.7 days / month
- Probability ~42% of days
- Intensity Up to ~50mm (P95)
Washout conditions are possible on ~13 days. Outdoor plans can become unreliable, so keep an indoor backup and flexibility around start times.
Rain High impact
Heavy rain days Measures: Heavy rain days (>=10mm). Observed about 30% of days (8.9 days/month) in September. Historical risk signal only, not a day-by-day forecast.
8.9 days / month
~30% of days
Why this matters
- Expected days 8.9 days / month
- Probability ~30% of days
- Intensity Up to ~63mm (P95)
Heavy rain is possible on ~9 days. Outdoor plans can become unreliable, so keep an indoor backup and flexibility around start times.
Rain High impact
Washout run Measures: Multi-day washout runs. Observed about 3.0 days/month in September. Historical risk signal only, not a day-by-day forecast.
3.0 days / month
Probability unavailable
Why this matters
- Expected days 3.0 days / month
- Probability —
- Intensity Up to ~71mm (P95)
Multi-day washout runs are possible on ~3 days. Outdoor plans can become unreliable, so keep an indoor backup and flexibility around start times.
Rain High impact
Very heavy rain Measures: Very heavy rain days (>=25mm). Observed about 9% of days (2.7 days/month) in September. Historical risk signal only, not a day-by-day forecast.
2.7 days / month
~9% of days
Why this matters
- Expected days 2.7 days / month
- Probability ~9% of days
- Intensity Up to ~86mm (P95)
Very heavy rain is possible on ~3 days. Outdoor plans can become unreliable, so keep an indoor backup and flexibility around start times.
Rain High impact
Extreme rain Measures: Extreme rain days (>=50mm). Observed about 2% of days (0.7 days/month) in September. Historical risk signal only, not a day-by-day forecast.
0.7 days / month
~2% of days
Why this matters
- Expected days 0.7 days / month
- Probability ~2% of days
- Intensity Up to ~101mm (P95)
Extreme rain is possible on ~1 days. Outdoor plans can become unreliable, so keep an indoor backup and flexibility around start times.
Wind High impact
Stormy conditions Measures: Storm-impact proxy days. Observed about 1% of days (0.4 days/month) in September. Historical risk signal only, not a day-by-day forecast.
0.4 days / month
~1% of days
Why this matters
- Expected days 0.4 days / month
- Probability ~1% of days
- Intensity Up to ~94km/h (P95)
Stormy conditions are possible on ~0 days. Exposed activities and transport links are more likely to be disrupted, so keep sheltered alternatives ready.
Wind High impact
Strong gusts Measures: Strong gust days (>=60 km/h). Observed about 1% of days (0.3 days/month) in September. Historical risk signal only, not a day-by-day forecast.
0.3 days / month
~1% of days
Why this matters
- Expected days 0.3 days / month
- Probability ~1% of days
- Intensity Up to ~97km/h (P95)
Strong gusts are possible on ~0 days. Exposed activities and transport links are more likely to be disrupted, so keep sheltered alternatives ready.
Visibility Moderate
Fog-likely signal Measures: Fog-likely visibility proxy. Observed about 15% of days (4.4 days/month) in September. Historical risk signal only, not a day-by-day forecast.
4.4 days / month
~15% of days
Why this matters
- Expected days 4.4 days / month
- Probability ~15% of days
- Intensity Up to ~95% (P95)
Fog-likely conditions are possible on ~4 days. Fixed-time outdoor plans are safer with a backup option and flexible timing.
Heat Moderate
Heatwave run Measures: Heatwave runs (>=3 hot days). Observed about 2.8 days/month in September. Historical risk signal only, not a day-by-day forecast.
2.8 days / month
Probability unavailable
Why this matters
- Expected days 2.8 days / month
- Probability —
- Intensity Up to ~34°C (P95)
Heatwave runs are possible on ~3 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 2.2 days/month in September. Historical risk signal only, not a day-by-day forecast.
2.2 days / month
Probability unavailable
Why this matters
- Expected days 2.2 days / month
- Probability —
- Intensity Up to ~41°C (P95)
Feels-like heatwave runs are possible on ~2 days. Midday activity often needs adjustment around shade, hydration, and indoor fallback options.
Humidity Minor
Humid days Measures: Humid days (dew point >=18C). Observed about 99% of days (29.6 days/month) in September. Historical risk signal only, not a day-by-day forecast.
29.6 days / month
~99% of days
Why this matters
- Expected days 29.6 days / month
- Probability ~99% of days
- Intensity Up to ~26°C (P95)
Humid conditions are possible on ~30 days. Comfort and pace can drop quickly, so plan shorter outdoor blocks with air-conditioned backup stops.
Heat Minor
Warm nights Measures: Warm nights (min >=22C). Observed about 93% of days (27.8 days/month) in September. Historical risk signal only, not a day-by-day forecast.
27.8 days / month
~93% of days
Why this matters
- Expected days 27.8 days / month
- Probability ~93% of days
- Intensity Up to ~26°C (P95)
Warm nights are possible on ~28 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 78% of days (23.5 days/month) in September. Historical risk signal only, not a day-by-day forecast.
23.5 days / month
~78% of days
Why this matters
- Expected days 23.5 days / month
- Probability ~78% of days
- Intensity Up to ~93% (P95)
High humidity is possible on ~23 days. Comfort and pace can drop quickly, so plan shorter outdoor blocks with air-conditioned backup stops.
Rain Minor
Wet days Measures: Wet days (>=0.1mm). Observed about 77% of days (23.2 days/month) in September. Historical risk signal only, not a day-by-day forecast.
23.2 days / month
~77% of days
Why this matters
- Expected days 23.2 days / month
- Probability ~77% of days
- Intensity Up to ~36mm (P95)
Measurable rain is possible on ~23 days. Fixed-time outdoor plans are safer with a backup option and flexible timing.
Cloud Minor
Cloudy days Measures: Cloudy days (cloud cover >=60%). Observed about 69% of days (20.8 days/month) in September. Historical risk signal only, not a day-by-day forecast.
20.8 days / month
~69% of days
Why this matters
- Expected days 20.8 days / month
- Probability ~69% of days
- Intensity Up to ~100% (P95)
Cloudy skies are possible on ~21 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 69% of days (20.6 days/month) in September. Historical risk signal only, not a day-by-day forecast.
20.6 days / month
~69% of days
Why this matters
- Expected days 20.6 days / month
- Probability ~69% of days
- Intensity Up to ~23h (P95)
Several rainy hours are possible on ~21 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 56% of days (16.9 days/month) in September. Historical risk signal only, not a day-by-day forecast.
16.9 days / month
~56% of days
Why this matters
- Expected days 16.9 days / month
- Probability ~56% of days
- Intensity Up to ~23h (P95)
Wet-most-of-day conditions are possible on ~17 days. Outdoor plans can become unreliable, so keep an indoor backup and flexibility around start times.
Cloud Minor
Mostly cloudy days Measures: Mostly cloudy days (cloud cover >=80%). Observed about 53% of days (15.8 days/month) in September. Historical risk signal only, not a day-by-day forecast.
15.8 days / month
~53% of days
Why this matters
- Expected days 15.8 days / month
- Probability ~53% of days
- Intensity Up to ~100% (P95)
Mostly cloudy skies are possible on ~16 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 43% of days (13.0 days/month) in September. Historical risk signal only, not a day-by-day forecast.
13.0 days / month
~43% of days
Why this matters
- Expected days 13.0 days / month
- Probability ~43% of days
- Intensity Up to ~26°C (P95)
Convective risk signal appears on ~13 days. Fixed-time outdoor plans are safer with a backup option and flexible timing.
Cloud Minor
Overcast days Measures: Overcast days (cloud cover >=95%). Observed about 31% of days (9.4 days/month) in September. Historical risk signal only, not a day-by-day forecast.
9.4 days / month
~31% of days
Why this matters
- Expected days 9.4 days / month
- Probability ~31% of days
- Intensity Up to ~100% (P95)
Overcast skies are possible on ~9 days. Fixed-time outdoor plans are safer with a backup option and flexible timing.
Heat Minor
Hot nights Measures: Hot nights (min >=25C). Observed about 29% of days (8.6 days/month) in September. Historical risk signal only, not a day-by-day forecast.
8.6 days / month
~29% of days
Why this matters
- Expected days 8.6 days / month
- Probability ~29% of days
- Intensity Up to ~27°C (P95)
Hot nights are possible on ~9 days. Midday activity often needs adjustment around shade, hydration, and indoor fallback options.
Other Minor
Low visibility proxy: same as fog-likely (RH ≥90% AND cloud ≥95%) — true visibility requires hourly visibility data Measures: Low visibility proxy: same as fog-likely (RH ≥90% AND cloud ≥95%) — true visibility requires hourly visibility data. Observed about 15% of days (4.4 days/month) in September. Historical risk signal only, not a day-by-day forecast.
4.4 days / month
~15% of days
Why this matters
- Expected days 4.4 days / month
- Probability ~15% of days
- Intensity Up to ~95 (P95)
Low visibility proxy: same as fog-likely (RH ≥90% AND cloud ≥95%) — true visibility requires hourly visibility data is possible on ~4 days. Fixed-time outdoor plans are safer with a backup option and flexible timing.
Wind Minor
Gusty days Measures: Gusty days (>=40 km/h). Observed about 5% of days (1.4 days/month) in September. Historical risk signal only, not a day-by-day forecast.
1.4 days / month
~5% of days
Why this matters
- Expected days 1.4 days / month
- Probability ~5% of days
- Intensity Up to ~77km/h (P95)
Gusty conditions are possible on ~1 days. Exposed activities and transport links are more likely to be disrupted, so keep sheltered alternatives ready.
Frequently asked questions
Is September a good time to visit Hanoi?
Typical September days in Hanoi reach highs of 30°C (86°F) with nights around 24°C (75°F). It usually feels hot by day and warm after dark. It is among the wetter months, so it is wise to have some indoor backup plans or flexible activities.
What are temperatures like in September?
Daytime temperatures in September typically peak near 30°C (86°F), while nights drop to around 24°C (75°F). Expect hot afternoons and warm evenings.
How much does it rain in September?
Rainfall in September averages 266 mm (10.5 in) across roughly 21 days. Overall it is a very wet 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 05:43 and sunset near 17:59. 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 7 km/h (4 mph), with gusts on the windiest days reaching about 34 km/h (21 mph). On the ground, it is a gentle to moderate breeze is common, but stronger winds are not frequent.