Ha Long weather in September

In September, Ha Long sees average daytime highs of 30°C and overnight lows near 25°C, with 243 mm of rain across 20 wet days and about 12.1 hours of daylight. It is the 4th-warmest and 4th-wettest month of the year here.

Day-to-day highs hold fairly steady near 30°C through the month. The sky is clear or mostly clear about 22% of the time in September, and the air most often feels miserable.

Daylight stretches from about 12 h 24 min at the start of September to 11 h 48 min by month's end. Set against the rest of the year, September is Ha Long's 4th-clearest and 11th-windiest month. For the whole year in context, see Ha Long's year-round climate.

Daytime high
30°
4th warmest
Overnight low
25°
9th coldest
Rainfall
243 mm
20 wet days
Daylight
12 h 06 min
5:42 AM – 5:50 PM
Cloud cover
69%
4th clearest
Wind
9 km/h
11th windiest
Solar energy
4.55 kWh/m²
Travel score
3.6
out of 10

Ha Long is provincial city of Vietnam.

Air quality
Elevated
PM10 47 µg/m³ · 2015
Density
993/km²
people per km²

Air quality: WHO Ambient Air Quality Database. Density & description: Wikidata (CC0), GeoNames.

Temperature in September

Average highAverage lowShaded bands: 10–90% of days

Day-to-day highs hold fairly steady near 30°C through the month.

A typical September day in Ha Long reaches about 30°C in the afternoon and slips back to 25°C overnight — a 5°C spread between the day's warmth and the night's chill. On most days the high lands between 28°C and 33°C. Set against its neighbours, September runs on par with August and about 2°C warmer than October.

20°25°30°35°151015202530
Avg high (°C)Avg low (°C)
13126
23126
33126
43125
53125
63125
73125
83125
93125
103025
113025
123025
133025
143025
153025
163025
173025
183025
193025
203025
213025
223025
233025
243024
253024
263024
273024
283024
293024
303024

How September really feels in Ha Long

Once humidity and wind are folded in, September averages 30 days that feel above 32°C and 0 that feel at or below 0°C — the comfort signal a plain temperature reading hides.

Days feeling ≥ 32°C
30
heat index over the day's high
Days feeling ≤ C
0
wind chill below the day's low

The story in September is heat — humidity pushes the afternoon "feels like" well above the raw temperature.

Ha Long weather by month

How September compares with the rest of the year at a glance. September is the 4th-warmest and 4th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°C)Rainfall (mm)Wet daysDaylight (hours)Travel score
Jan19° / 15°346.510.96.3
Feb20° / 16°215.611.36.4
Mar22° / 18°448.811.96.5
Apr26° / 22°6911.612.56.0
May30° / 25°21919.5133.9
Jun31° / 27°26622.413.22.9
Jul31° / 27°30524.313.12.8
Aug31° / 26°38126.212.72.7
Sep30° / 25°2432012.13.6
Oct28° / 23°10411.911.55.7
Nov25° / 19°518.2117.1
Dec21° / 16°315.910.87.0

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 22% of the time in September.

Beyond those clear spells, partly cloudy skies cover about 14% of September, with mostly cloudy or overcast conditions the remaining 64%. Skies tend to open up as the month goes on.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
12377
22377
32476
42476
52575
62575
72674
82674
92872
102872
112971
123169
133268
143367
153565
163664
173763
183961
194060
204258
214357
224357
234555
244654
254753
264852
274951
284951
295149
305248

Chance of precipitation in September

Any precipitation

Ha Long gets around 243 mm of rain over 20 wet days in September. The line is the day-by-day chance of measurable precipitation.

Day to day, the chance of measurable rain averages around 67% and peaks near 84% on the wettest days. The odds ease toward the end of the month.

0%20%40%60%80%151015202530
Rain chance (%)
184
284
383
483
582
681
780
878
977
1076
1174
1272
1371
1469
1567
1665
1763
1862
1960
2058
2157
2256
2355
2454
2553
2652
2751
2850
2950
3049

Humidity in September

DryComfortableHumidMuggyOppressiveMiserable

Most of September feels miserable — the stacked bands show each day's mix of comfort levels, read off the dew point.

By dew point, September lands in the miserable band about 63% of days. Sticky, muggy-or-worse air turns up on roughly 97% of them.

0%25%50%75%100%151015202530
Comfortable (%)Humid (%)Muggy (%)Oppressive (%)Miserable (%)
10001189
20011287
30011386
40111484
50111583
60121681
70121681
80131779
90231877
100241876
110251974
120261973
130262072
140372169
150382267
160392266
1703102463
1803112561
1904122658
2004132855
2104142953
2204143151
2304153348
2404163445
2505163643
2605163840
2716173938
2816174036
2917174133
3018184231

Wind in September

Winds average 9 km/h in September.

Across September, daily wind ranges from about 8 km/h on the calmest days to 10 km/h at its breeziest. It stays fairly steady from day to day.

051015151015202530
Wind speed (km/h)Feels
18calm
28calm
38calm
48calm
58calm
68calm
78calm
88calm
99calm
109calm
119calm
129calm
139calm
149calm
159calm
169calm
179calm
189calm
199calm
209calm
219calm
2210calm
2310calm
2410calm
2510calm
2610calm
2710calm
2810calm
2910calm
3010calm

Sunrise & sunset in September

DaylightNight

Daylight runs from about 12 h 24 min at the start of September to 11 h 48 min by month's end. The lit band spans sunrise to sunset each day.

Days shrink by about 36 minutes over September. Sunrise moves from 5:39 AM to 5:46 AM, and sunset from 6:04 PM to 5:36 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
112.45:396:04
212.45:396:03
312.45:396:02
412.45:406:01
512.35:406:00
612.35:405:59
712.35:405:58
812.35:415:57
912.35:415:56
1012.25:415:55
1112.25:415:55
1212.25:425:54
1312.25:425:53
1412.25:425:52
1512.15:425:51
1612.15:425:50
1712.15:435:49
1812.15:435:48
1912.15:435:47
2012.05:435:46
2112.05:445:45
2212.05:445:44
2312.05:445:43
2412.05:445:42
2511.95:455:41
2611.95:455:40
2711.95:455:39
2811.95:465:38
2911.95:465:37
3011.85:465:36

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 4.55 kWh/m².

For context, solar energy here swings from a low near 2.58 kWh/m² to a high of 5.07 kWh/m² in May across the year — September's 4.55 kWh/m² falls in the middle.

024151015202530
Solar energy (kWh/m²)Level
14.5Bright
24.5Bright
34.5Bright
44.5Bright
54.5Bright
64.5Bright
74.5Bright
84.5Bright
94.5Bright
104.5Bright
114.5Bright
124.5Bright
134.5Bright
144.5Bright
154.6Bright
164.6Bright
174.6Bright
184.6Bright
194.6Bright
204.6Bright
214.6Bright
224.6Bright
234.7Bright
244.7Bright
254.7Bright
264.7Bright
274.7Bright
284.6Bright
294.6Bright
304.6Bright
Planning a trip in September

Hazard calendar for Ha Long

In seasonPeak

In September, Ha Long sits inside its pacific typhoon and monsoon season. The full year is below, with each hazard's peak months called out.

Ha Long sits in the Pacific typhoon belt; the season peaks July–October.

Ha Long's monsoon runs May–September, when most of the year's rain falls.

Pacific typhoon
Monsoon
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec

Is September a good time to visit Ha Long?

Our two travel scores rate September for general sightseeing and for beach or pool weather — 0 (poor) to 10 (ideal).

3.6
Sightseeing
9th-best month of the year
5.1
Beach & pool
5th-best month of the year

September is a weaker month for outdoor sightseeing in Ha Long.

What to pack for Ha Long in September

From September's temperature range, rain chance, sun and wind — what's worth putting in the bag.

In September, Ha Long sees daytime highs around 30°C and nights near 25°C. Pack light clothes and rain gear. Worth having: sun protection. About 20 days see rain.

light clothesrain gearsun protection

Sea temperature near Ha Long in September

The nearest coast averages about 29°C in September — the other half of the beach question. The full-year curve and swim-comfort zones are below.

The sea at the nearest coast (about 32 km away) is warmest in August at about 30°C and coldest in February near 19°C.

It's comfortable for a long swim from Mar 13 to Jan 10 — about 10 months when the water holds above 20°C.

20°25°30°JanFebMarAprMayJunJulAugSepOctNovDeccoolrefreshingwarmtropicalcomfortable to swim
Sea temperature (°C)Comfort
Jan20Cool
Feb19Cool
Mar20Refreshing
Apr23Refreshing
May27Warm
Jun29Tropical
Jul29Tropical
Aug30Tropical
Sep29Tropical
Oct28Warm
Nov25Warm
Dec22Refreshing

UV index in Ha Long in September

LowModerateHighVery highExtreme

Clear-sky midday UV in September peaks around 9 (very high — sun protection essential). The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in Ha Long peaks around July 12 at about 12 (extreme) — sunscreen, a hat and midday shade are essential. It bottoms out near December 19 at about 6 (high).

The index reaches 3 or more — the level where the WHO recommends sun protection — every month of the year.

025710JanFebMarAprMayJunJulAugSepOctNovDecVery highExtremeVery highHighJul 12UV 12Dec 19UV 6
UV index (midday)Level
Jan7High
Feb8Very high
Mar9Very high
Apr8Very high
May10Extreme
Jun12Extreme
Jul12Extreme
Aug9Very high
Sep9Very high
Oct9Very high
Nov7High
Dec6High

Air quality in Ha Long in September

GoodModeratePoorUnhealthyVery unhealthy

Average fine-particle pollution (PM2.5) through the year — so you can see where September falls, not just the annual average.

Air quality in Ha Long is worst in January — around 42 µg/m³ PM2.5 (poor), about 2.6× the cleanest month (July, 16 µg/m³).

Modeled monthly averages (CAMS reanalysis, 2015–2024).

0204060JanFebMarAprMayJunJulAugSepOctNovDecPoorModeratePoorJan 2342 µg/m³Jul 1716 µg/m³
PM2.5 (µg/m³)Level
Jan42Poor
Feb42Poor
Mar41Poor
Apr40Poor
May26Moderate
Jun19Moderate
Jul16Moderate
Aug18Moderate
Sep21Moderate
Oct27Moderate
Nov29Moderate
Dec39Poor
Location & terrain

Where is Ha Long?

Ha Long sits at 21.0°N, 107.1°E, 8 m above sea level, in Vietnam. The nearest listed city is Cẩm Phả, 22 km away.

Topography around Ha Long

How much the land rises and falls, and what covers it, within 3, 16 and 80 km of Ha Long.

Within 3 km, the terrain around Ha Long has only modest variations in elevation — a maximum elevation change of 150 m around an average of 9 m above sea level; within 16 km, large variations in elevation — a maximum elevation change of 679 m; within 80 km, very significant variations in elevation — a maximum elevation change of 1,530 m.

The land around Ha Long is covered by water (57%) and artificial surfaces (21%) within 3 km, water (46%) and trees (37%) within 16 km, and trees (42%) and water (42%) within 80 km.

3 km
150 m
16 km
679 m
80 km
1,530 m
treesgrasslandcroplandartificial surfacesbare terrainwatermangroves
September weather nearby: Cẩm Phả 22 km · Cẩm Phả Mines 25 km · Cát Bà 25 km · Thành Phố Uông Bí 33 km · Đố Sơn 40 km · Haiphong 42 km · Thị Trấn Ba Chẽ 42 km · Kiến An 49 km

Vietnam travel facts

Travel advisory
Level 1
Exercise Normal Precautions
Power plugs
Type A / B / C / F
220 V · 50 Hz
Prices
≈ 29% of US
price level, 2025
GDP per capita
$5,066
2025
Happiness
6.4 / 10
World Happiness, 2025
Safe drinking water
59%
of population, 2024
Homicide rate
1.5
per 100k, 2011
Road deaths
30.6
per 100k/yr, 2019
Income group
Upper middle
World Bank
English
Moderate
EF EPI 500
Religion
none 86%Catholic 6%Buddhist 6%Protestant 1%

Sources: World Bank, US State Department, World Happiness Report, WHO/UNICEF, EF EPI, CIA World Factbook.

Data sources

Temperature, precipitation, cloud, humidity, wind and solar figures are a 1991–2020 climatology for Ha Long (20.9505°, 107.0734°, elevation 8 m), computed from hourly ERA5 reanalysis — contains modified Copernicus Climate Change Service information. Sun figures are astronomical calculations, not observations. City data © GeoNames, CC BY 4.0. Map outlines from Natural Earth (public domain); interactive map © Google. Tropical-cyclone seasons are the published climatological basin seasons (NOAA National Hurricane Center / regional warning centres). Sea temperatures are the NOAA OISST v2.1 1991–2020 monthly climatology (public domain), sampled at the nearest ocean point. UV index is derived from CAMS (Copernicus Atmosphere Monitoring Service) clear-sky UV data — contains modified Copernicus Atmosphere Monitoring Service information. Monthly air-quality (PM2.5) seasonality is from the CAMS EAC4 reanalysis (Copernicus Atmosphere Monitoring Service), scaled to the WHO annual mean where available. Topography is sampled from the Copernicus DEM GLO-90 elevation model (© ESA/Airbus) and ESA WorldCover 2021 land cover (CC BY 4.0).