Lạng Sơn weather in September

In September, Lạng Sơn sees average daytime highs of 29°C and overnight lows near 23°C, with 164 mm of rain across 18.3 wet days and about 12.1 hours of daylight. It is the 4th-warmest and 5th-wettest month of the year here.

Day-to-day highs hold fairly steady near 29°C through the month. The sky is clear or mostly clear about 21% of the time in September, and the air most often feels oppressive.

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 Lạng Sơn's 4th-clearest and 11th-windiest month. For the whole year in context, see Lạng Sơn's year-round climate.

Daytime high
29°
4th warmest
Overnight low
23°
9th coldest
Rainfall
164 mm
18.3 wet days
Daylight
12 h 06 min
5:44 AM – 5:51 PM
Cloud cover
69%
4th clearest
Wind
8 km/h
11th windiest
Solar energy
4.46 kWh/m²
Travel score
4.2
out of 10

Lạng Sơn is provincial city of Vietnam.

Density
2,533/km²
people per km²
Founded
2002

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 29°C through the month.

A typical September day in Lạng Sơn reaches about 29°C in the afternoon and slips back to 23°C overnight — a 7°C spread between the day's warmth and the night's chill. On most days the high lands between 26°C and 32°C. Set against its neighbours, September runs about 1°C cooler than August and about 3°C warmer than October.

15°20°25°30°35°151015202530
Avg high (°C)Avg low (°C)
13024
23024
33024
43024
53024
63024
73024
83024
93024
103023
113023
123023
133023
143023
153023
162923
172923
182923
192923
202923
212923
222923
232922
242922
252922
262922
272922
282922
292922
302922

How September really feels in Lạng Sơn

Once humidity and wind are folded in, September averages 20 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
20
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.

Lạng Sơn weather by month

How September compares with the rest of the year at a glance. September is the 4th-warmest and 5th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°C)Rainfall (mm)Wet daysDaylight (hours)Travel score
Jan17° / 11°5711.110.85.1
Feb19° / 13°4410.111.25.6
Mar21° / 16°7914.411.85.5
Apr26° / 20°9714.912.55.5
May29° / 23°22121.2134.0
Jun30° / 25°25723.613.33.0
Jul31° / 25°27024.913.22.9
Aug30° / 24°28525.312.73.0
Sep29° / 23°16418.312.14.2
Oct27° / 20°7510.911.56.4
Nov23° / 16°507.9117.1
Dec19° / 12°458.210.76.3

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 21% of the time in September.

Beyond those clear spells, partly cloudy skies cover about 16% 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 (%)
12773
22773
32773
42674
52674
62773
72773
82773
92971
102971
113070
123169
133367
143367
153664
163763
173862
183961
193961
204159
214258
224357
234555
244654
254753
264753
274852
284951
295050
305149

Chance of precipitation in September

Any precipitation

Lạng Sơn gets around 164 mm of rain over 18.3 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 60% and peaks near 74% on the wettest days. The odds ease toward the end of the month.

0%20%40%60%80%151015202530
Rain chance (%)
174
273
373
472
572
671
771
870
969
1068
1167
1266
1365
1463
1562
1661
1759
1858
1956
2055
2154
2252
2351
2450
2549
2648
2747
2847
2946
3045

Humidity in September

DryComfortableHumidMuggyOppressiveMiserable

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

By dew point, September lands in the oppressive band about 53% of days. Sticky, muggy-or-worse air turns up on roughly 92% of them.

0%25%50%75%100%151015202530
Comfortable (%)Humid (%)Muggy (%)Oppressive (%)Miserable (%)
10035344
20045343
30045442
40155341
50155539
61165438
71175536
81285435
91295533
1012105532
1113115530
1213125529
1314135527
1414145625
1515155524
1616165522
1717175520
1827185419
1928195318
2028215217
2129225215
2229235214
23210245113
24210255112
25311264911
26311274910
2741227489
2841228488
2951328477
3051329466

Wind in September

Winds average 8 km/h in September.

Across September, daily wind ranges from about 7 km/h on the calmest days to 9 km/h at its breeziest. It stays fairly steady from day to day.

051015151015202530
Wind speed (km/h)Feels
17calm
27calm
37calm
47calm
57calm
67calm
77calm
87calm
97calm
108calm
118calm
128calm
138calm
148calm
158calm
168calm
178calm
188calm
198calm
208calm
218calm
228calm
239calm
249calm
259calm
269calm
279calm
289calm
299calm
309calm

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 5:48 AM, and sunset from 6:06 PM to 5:37 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
112.45:396:06
212.45:406:05
312.45:406:04
412.45:406:03
512.45:416:02
612.35:416:01
712.35:416:00
812.35:415:59
912.35:425:58
1012.35:425:57
1112.25:425:56
1212.25:425:55
1312.25:435:54
1412.25:435:53
1512.15:435:52
1612.15:445:51
1712.15:445:50
1812.15:445:49
1912.15:445:48
2012.05:455:47
2112.05:455:46
2212.05:455:45
2312.05:465:44
2412.05:465:43
2511.95:465:42
2611.95:465:41
2711.95:475:40
2811.95:475:39
2911.85:475:38
3011.85:485:37

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 4.46 kWh/m².

For context, solar energy here swings from a low near 2.23 kWh/m² to a high of 4.72 kWh/m² in July across the year — September's 4.46 kWh/m² falls in the middle.

024151015202530
Solar energy (kWh/m²)Level
14.5Bright
24.4Bright
34.4Bright
44.4Bright
54.4Bright
64.4Bright
74.4Bright
84.4Bright
94.4Bright
104.4Bright
114.4Bright
124.5Bright
134.5Bright
144.5Bright
154.5Bright
164.5Bright
174.5Bright
184.5Bright
194.5Bright
204.5Bright
214.5Bright
224.5Bright
234.5Bright
244.5Bright
254.5Bright
264.5Bright
274.5Bright
284.5Bright
294.5Bright
304.5Bright
Planning a trip in September

Hazard calendar for Lạng Sơn

In seasonPeak

In September, Lạng Sơn sits inside its monsoon season. The full year is below, with each hazard's peak months called out.

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

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

Is September a good time to visit Lạng Sơn?

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

4.2
Sightseeing
8th-best month of the year
5.5
Beach & pool
3rd-best month of the year

September is a reasonable time to visit Lạng Sơn for sightseeing.

What to pack for Lạng Sơn in September

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

In September, Lạng Sơn sees daytime highs around 29°C and nights near 23°C. Pack light clothes and rain gear. About 18 days see rain.

light clothesrain gear

UV index in Lạng Sơn in September

LowModerateHighVery highExtreme

Clear-sky midday UV in September peaks around 10 (very high — sun protection essential). The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in Lạng Sơn peaks around June 23 at about 12 (extreme) — sunscreen, a hat and midday shade are essential. It bottoms out near December 14 at about 6 (high).

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

025710JanFebMarAprMayJunJulAugSepOctNovDecHighVery highVery highExtremeVery highHighJun 23UV 12Dec 14UV 6
UV index (midday)Level
Jan6High
Feb7High
Mar9Very high
Apr7High
May9Very high
Jun12Extreme
Jul12Extreme
Aug10Extreme
Sep10Very high
Oct8Very high
Nov6High
Dec6High

Air quality in Lạng Sơn 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 Lạng Sơn is worst in December — around 58 µg/m³ PM2.5 (unhealthy), about 2.3× the cleanest month (July, 25 µg/m³).

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

0204060JanFebMarAprMayJunJulAugSepOctNovDecUnhealthyPoorModeratePoorUnhealthyDec 2358 µg/m³Jul 1625 µg/m³
PM2.5 (µg/m³)Level
Jan57Unhealthy
Feb55Unhealthy
Mar55Poor
Apr54Poor
May37Poor
Jun29Moderate
Jul25Moderate
Aug29Moderate
Sep36Poor
Oct43Poor
Nov50Poor
Dec58Unhealthy
Location & terrain

Where is Lạng Sơn?

Lạng Sơn sits at 21.9°N, 106.8°E, 265 m above sea level, in Vietnam. The nearest listed city is Thị Trấn Na Dương, 26 km away.

Topography around Lạng Sơn

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

Within 3 km, the terrain around Lạng Sơn has only modest variations in elevation — a maximum elevation change of 171 m around an average of 282 m above sea level; within 16 km, large variations in elevation — a maximum elevation change of 978 m; within 80 km, very significant variations in elevation — a maximum elevation change of 1,481 m.

The land around Lạng Sơn is covered by trees (46%) and artificial surfaces (32%) within 3 km, trees (80%) within 16 km, and trees (89%) within 80 km.

3 km
171 m
16 km
978 m
80 km
1,481 m
treesgrasslandcroplandartificial surfacesbare terrainwater
September weather nearby: Thị Trấn Na Dương 26 km · Thị Trấn Thất Khê 54 km · Chũ 57 km · Thị Trấn Ba Chẽ 84 km · Bắc Giang 87 km · Thị Trấn Tiên Yên 88 km · Thị Trấn Đông Triều 89 km · Thị Trấn Mạo Khê 90 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 Lạng Sơn (21.8526°, 106.761°, elevation 265 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. 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).