Lang Son climate — normals and trends

Q: What is the climate of Lang Son?

Lang Son has a humid subtropical climate (Köppen Cfa). Over 1940-2025, the average annual temperature is 21.4 °C and it receives 1,717 mm of precipitation per year.

Q: What is the hottest day ever recorded in Lang Son?

The hottest day measured in Lang Son between 1940 and 2025 was 30 July 1946, reaching 39.1 °C.

Q: What is the coldest day in Lang Son?

The coldest day measured in Lang Son between 1940 and 2025 was 12 January 1955, at 1.0 °C.

Q: Does it snow in Lang Son?

Almost never: Lang Son sees virtually no snow, with about 0 frost days per year.

Q: Has the climate of Lang Son warmed?

Yes: Lang Son warmed by +1.1 °C between 1940 and 2025, a statistically significant trend.

Q: What is the wettest day in Lang Son?

The wettest day measured in Lang Son between 1940 and 2025 was 11 August 1962, with 226 mm of rain in 24 hours.

Q: What was the windiest day in Lang Son?

The windiest day measured in Lang Son between 1940 and 2025 was 23 July 1980, with winds reaching 51.6 km/h.

Q: What is the warmest month in Lang Son?

The warmest month in Lang Son is July (27.0 °C on average); the coldest is January (13.7 °C).

Q: How much does it rain in Lang Son?

Lang Son receives on average 1,717 mm of precipitation per year, spread over about 200 rainy days.

Q: Is it sunny in Lang Son?

Lang Son gets on average 7.1 hours of sunshine per day, roughly 2,592 hours per year over 1940-2025.

Lang Son (Vietnam) has a humid subtropical climate (Cfa) under the Köppen-Geiger classification. Its mean annual temperature is 21.4 °C and it receives 1,717 mm of precipitation per year.

These figures are normals computed over 86 complete calendar years, from 1940 to 2025, using ERA5 reanalysis data from the Copernicus programme.

The warmest month is July (27.0 °C on average) and the coldest is January (13.7 °C). Rainfall peaks in August.

Lang Son averages 0 frost days, 83 hot days (≥ 30 °C) and 200 rainy days per year.

Lang Son has warmed by +1.1 °C between 1940 and 2025, or +0.13 °C per decade. This trend is statistically significant.

The hottest day of the period reached 39.1 °C (on 30 July 1946) and the coldest 1.0 °C (on 12 January 1955).

Data from ERA5 reanalysis (Copernicus Climate Change Service), redistributed under a CC-BY 4.0 licence. Normals are recomputed whenever the archive is updated.

Climate normals · ERA5

Lang SonLạng Sơn Province

coords: 21.85°, 106.76°
period: 1940–2025 · 86 yrs

CfaHumid subtropicalWarmest monthJulyColdest monthJanuaryWettest monthAugustDriest monthDecember

Mean daily temperature

21.4°C

Average daily high

25.1°C

Average daily low

18.6°C

Annual rainfall

1,717mm

Sunshine / day

7.1h

Mean relative humidity

82%

Average peak wind

14.5km/h

Seasonal range

13.3°C

Frost days (< 0 °C)

0 d/yr

Hot days (≥ 30 °C)

83 d/yr

Rainy days (≥ 1 mm)

200 d/yr

Annual snowfall

0.0 cm

Average feels-like high

27.6 °C

Average feels-like low

20.2 °C

Average peak gust

34.4 km/h

Tropical nights (≥ 20 °C)

185 d/yr

Solar radiation

13.4 MJ/m²

Has the climate changed?

One stripe per year, 1940 to 2025

+1.1 °C

since 1940

+0.1 °C per decade · r² = 0.32 · p = < 0.001

19402025

Trend fitted by linear regression (ordinary least squares) on annual means. A trend is shown only when it is statistically significant (p < 0.05).

A climograph overlays rainfall (bars) and temperature (line): the standard reading in climatology, where you can see at a glance whether the warm season is also the dry one.

Records for the period

Hottest day

39.1 °C

30 July 1946

Coldest day

1.0 °C

12 January 1955

Wettest day

226 mm

11 August 1962

Windiest day

51.6 km/h

23 July 1980

Strongest gust

130.7 km/h

23 July 1980

Hottest feels-like

45.3 °C

16 May 2013

Coldest feels-like

-4.4 °C

24 January 2016

Snowiest day

1.0 cm

24 January 2016

Sunniest day

13.1 h

14 June 1981

Year	Hottest day	Coldest day	Annual mean	Rainfall	Hot days
2025	34.8 °C30 July 2025	5.5 °C13 January 2025	22.1 °C	1,897 mm	108
2024	35.6 °C30 April 2024	4.6 °C24 January 2024	22.6 °C	1,991 mm	120
2023	36.1 °C22 May 2023	5.8 °C30 January 2023	22.7 °C	1,453 mm	121
2022	33.8 °C21 June 2022	4.8 °C20 February 2022	21.7 °C	1,805 mm	107
2021	35.8 °C20 June 2021	5.1 °C8 January 2021	22.4 °C	1,521 mm	129
2020	35.3 °C21 May 2020	6.5 °C17 December 2020	22.2 °C	1,506 mm	112
2019	35.5 °C19 May 2019	5.9 °C1 January 2019	22.5 °C	1,781 mm	113
2018	35.0 °C5 July 2018	4.3 °C31 December 2018	22.0 °C	1,860 mm	96
2017	37.4 °C3 June 2017	7.8 °C20 December 2017	22.0 °C	1,853 mm	90
2016	35.0 °C3 June 2016	1.6 °C24 January 2016	22.1 °C	1,589 mm	120
2015	36.4 °C30 May 2015	7.0 °C15 January 2015	22.5 °C	1,755 mm	114
2014	34.8 °C23 May 2014	4.5 °C13 February 2014	21.7 °C	1,835 mm	105
2013	36.1 °C16 May 2013	3.9 °C20 December 2013	21.5 °C	1,724 mm	86
2012	36.4 °C4 May 2012	4.8 °C5 January 2012	21.4 °C	1,865 mm	101
2011	35.0 °C31 August 2011	4.2 °C11 January 2011	20.5 °C	1,415 mm	93
2010	35.2 °C20 May 2010	5.9 °C17 December 2010	22.0 °C	1,726 mm	101
2009	34.5 °C20 June 2009	4.4 °C11 January 2009	22.2 °C	1,280 mm	120
2008	33.9 °C30 July 2008	3.0 °C1 February 2008	20.9 °C	1,762 mm	93
2007	34.9 °C24 May 2007	6.0 °C29 January 2007	21.8 °C	1,468 mm	98
2006	34.0 °C12 April 2006	6.9 °C7 January 2006	22.0 °C	1,594 mm	105
2005	34.0 °C12 May 2005	5.3 °C13 January 2005	21.5 °C	1,247 mm	108
2004	35.3 °C1 July 2004	4.5 °C9 February 2004	21.4 °C	1,219 mm	89
2003	35.9 °C7 May 2003	4.2 °C7 January 2003	22.3 °C	1,459 mm	105
2002	34.2 °C21 May 2002	3.6 °C27 December 2002	21.8 °C	1,814 mm	87
2001	34.9 °C21 April 2001	3.1 °C25 December 2001	21.4 °C	2,049 mm	75
2000	33.5 °C5 July 2000	4.6 °C2 February 2000	21.5 °C	1,486 mm	88
1999	34.5 °C6 June 1999	3.2 °C23 December 1999	21.7 °C	1,505 mm	99
1998	35.0 °C22 May 1998	5.3 °C20 January 1998	22.4 °C	1,290 mm	105
1997	35.0 °C9 June 1997	7.3 °C12 January 1997	21.5 °C	2,204 mm	67
1996	34.7 °C2 August 1996	2.8 °C21 February 1996	21.0 °C	1,856 mm	78
1995	34.0 °C25 May 1995	4.5 °C31 December 1995	21.2 °C	1,770 mm	75
1994	35.4 °C2 May 1994	5.9 °C20 January 1994	21.7 °C	1,976 mm	74
1993	33.9 °C4 June 1993	4.4 °C16 January 1993	21.4 °C	1,686 mm	99
1992	34.6 °C8 May 1992	6.3 °C17 January 1992	21.2 °C	1,506 mm	91
1991	34.2 °C24 May 1991	2.9 °C28 December 1991	21.9 °C	1,210 mm	100
1990	36.1 °C22 April 1990	5.4 °C1 February 1990	21.7 °C	1,838 mm	85
1989	34.3 °C18 June 1989	4.4 °C13 January 1989	21.1 °C	1,608 mm	87
1988	35.8 °C24 May 1988	4.4 °C19 February 1988	20.9 °C	1,709 mm	79
1987	34.7 °C21 May 1987	5.4 °C8 December 1987	22.3 °C	1,656 mm	102
1986	35.2 °C2 July 1986	3.5 °C1 March 1986	21.4 °C	2,057 mm	82
1985	34.0 °C6 May 1985	5.3 °C17 December 1985	20.8 °C	1,867 mm	96
1984	34.8 °C19 March 1984	4.1 °C9 January 1984	20.7 °C	1,648 mm	85
1983	35.4 °C13 July 1983	3.4 °C29 December 1983	21.0 °C	1,573 mm	114
1982	33.8 °C21 June 1982	1.8 °C27 December 1982	21.4 °C	1,965 mm	83
1981	34.4 °C21 July 1981	5.1 °C8 December 1981	21.5 °C	2,269 mm	94
1980	34.8 °C24 April 1980	3.9 °C7 February 1980	21.5 °C	1,946 mm	83
1979	34.7 °C29 July 1979	6.2 °C16 January 1979	21.6 °C	1,912 mm	78
1978	34.5 °C29 July 1978	5.4 °C18 January 1978	21.1 °C	2,405 mm	68
1977	34.4 °C9 June 1977	2.0 °C31 January 1977	21.1 °C	1,593 mm	85
1976	33.8 °C17 June 1976	3.8 °C29 December 1976	20.7 °C	1,644 mm	77
1975	33.5 °C30 July 1975	2.3 °C14 December 1975	21.3 °C	2,121 mm	92
1974	34.7 °C2 June 1974	2.3 °C1 January 1974	21.2 °C	1,712 mm	85
1973	36.9 °C8 April 1973	3.1 °C27 December 1973	22.0 °C	2,556 mm	92
1972	34.9 °C10 July 1972	3.7 °C8 February 1972	21.4 °C	2,143 mm	98
1971	35.1 °C18 May 1971	3.2 °C6 January 1971	21.0 °C	1,697 mm	67
1970	35.0 °C12 May 1970	4.8 °C7 January 1970	21.1 °C	1,674 mm	88
1969	36.2 °C13 May 1969	4.9 °C31 January 1969	21.5 °C	1,349 mm	113
1968	34.4 °C28 July 1968	3.5 °C14 February 1968	21.4 °C	1,767 mm	77
1967	35.0 °C30 August 1967	1.9 °C17 January 1967	20.8 °C	1,459 mm	91
1966	33.7 °C12 May 1966	3.7 °C27 December 1966	21.0 °C	1,931 mm	39
1965	33.5 °C21 July 1965	1.9 °C18 December 1965	20.9 °C	1,965 mm	46
1964	34.4 °C8 August 1964	3.1 °C19 December 1964	21.1 °C	1,605 mm	80
1963	33.7 °C6 September 1963	2.3 °C16 January 1963	21.2 °C	1,745 mm	75
1962	34.0 °C28 May 1962	5.4 °C27 January 1962	21.1 °C	1,698 mm	90
1961	34.3 °C26 August 1961	2.7 °C18 January 1961	21.6 °C	1,705 mm	89
1960	34.7 °C27 April 1960	3.1 °C24 January 1960	21.6 °C	1,830 mm	85
1959	34.3 °C30 August 1959	5.5 °C25 December 1959	21.2 °C	1,652 mm	62
1958	38.0 °C2 June 1958	2.5 °C2 February 1958	21.6 °C	1,665 mm	98
1957	35.3 °C16 August 1957	2.5 °C14 February 1957	21.5 °C	1,569 mm	93
1956	35.2 °C19 April 1956	3.2 °C9 January 1956	21.1 °C	1,392 mm	59
1955	34.1 °C15 April 1955	1.0 °C12 January 1955	21.2 °C	1,274 mm	40
1954	34.7 °C29 July 1954	4.4 °C26 January 1954	21.5 °C	1,342 mm	70
1953	33.5 °C13 August 1953	5.5 °C13 December 1953	21.4 °C	1,762 mm	68
1952	33.0 °C10 April 1952	2.3 °C19 February 1952	21.8 °C	2,021 mm	66
1951	32.8 °C10 April 1951	2.2 °C13 January 1951	21.1 °C	2,036 mm	41
1950	34.2 °C21 April 1950	4.4 °C14 February 1950	21.3 °C	1,980 mm	37
1949	36.7 °C14 June 1949	3.7 °C10 January 1949	21.8 °C	1,269 mm	70
1948	32.8 °C14 March 1948	2.6 °C26 January 1948	21.2 °C	1,772 mm	59
1947	32.6 °C18 July 1947	3.5 °C20 December 1947	20.8 °C	1,671 mm	38
1946	39.1 °C30 July 1946	5.5 °C8 January 1946	22.5 °C	784 mm	129
1945	31.8 °C14 July 1945	2.6 °C4 February 1945	19.8 °C	1,777 mm	26
1944	36.3 °C8 April 1944	2.7 °C22 December 1944	20.8 °C	1,847 mm	27
1943	33.8 °C29 May 1943	3.3 °C13 January 1943	20.6 °C	1,505 mm	41
1942	32.0 °C6 August 1942	4.5 °C13 February 1942	20.7 °C	2,145 mm	21
1941	32.8 °C26 April 1941	5.7 °C4 February 1941	20.8 °C	1,850 mm	20
1940	31.8 °C15 May 1940	3.6 °C25 January 1940	20.5 °C	1,717 mm	30

Normals computed over complete calendar years 1940–2025.

A specific year

Pick a year and see how it compares to normal — warmer, drier or more extreme than usual?

Year

Across the whole year

Average daily high

25.6 °C

+0.5 °C

Hot days (≥ 30 °C)

108 d/yr

+25

Frost days (< 0 °C)

0 d/yr

Annual rainfall

1897 mm

+180 mm

Month by month

	High	vs. normal	Precipitation	vs. normal
Jan	20.0 °C	+2.7 °C	16 mm	-36 mm
Feb	16.6 °C	-1.8 °C	47 mm	-9 mm
Mar	22.0 °C	+0.1 °C	70 mm	-8 mm
Apr	27.2 °C	+1.2 °C	95 mm	-17 mm
May	28.6 °C	-0.3 °C	218 mm	-6 mm
Jun	30.6 °C	+0.5 °C	270 mm	+1 mm
Jul	31.4 °C	+0.9 °C	307 mm	+54 mm
Aug	30.1 °C	0.0 °C	313 mm	+22 mm
Sep	30.3 °C	+1.3 °C	260 mm	+68 mm
Oct	27.1 °C	+0.8 °C	179 mm	+76 mm
Nov	21.7 °C	-1.3 °C	62 mm	+12 mm
Dec	21.1 °C	+1.9 °C	61 mm	+24 mm

The year's extremes

Hottest day

34.8 °C

30 Jul 2025

Coldest day

5.5 °C

13 Jan 2025

Wettest day

93.6 mm

6 Oct 2025

Windiest day

35.0 km/h

22 Jul 2025

Strongest gust

76.3 km/h

22 Jul 2025

Hottest feels-like

43.9 °C

30 Jul 2025

Coldest feels-like

2.8 °C

13 Jan 2025

Sunniest day

12.8 h

1 Jun 2025

What was the weather like that day?

Your birthday, a wedding, a memorable trip: discover the actual weather for any date since 1940.

Date

Frequently asked questions

What is the climate of Lang Son?

Lang Son has a humid subtropical climate (Köppen Cfa). Over 1940-2025, the average annual temperature is 21.4 °C and it receives 1,717 mm of precipitation per year.

What is the hottest day ever recorded in Lang Son?

The hottest day measured in Lang Son between 1940 and 2025 was 30 July 1946, reaching 39.1 °C.

What is the coldest day in Lang Son?

The coldest day measured in Lang Son between 1940 and 2025 was 12 January 1955, at 1.0 °C.

Does it snow in Lang Son?

Almost never: Lang Son sees virtually no snow, with about 0 frost days per year.

Has the climate of Lang Son warmed?

Yes: Lang Son warmed by +1.1 °C between 1940 and 2025, a statistically significant trend.

What is the wettest day in Lang Son?

The wettest day measured in Lang Son between 1940 and 2025 was 11 August 1962, with 226 mm of rain in 24 hours.

What was the windiest day in Lang Son?

The windiest day measured in Lang Son between 1940 and 2025 was 23 July 1980, with winds reaching 51.6 km/h.

What is the warmest month in Lang Son?

The warmest month in Lang Son is July (27.0 °C on average); the coldest is January (13.7 °C).

How much does it rain in Lang Son?

Lang Son receives on average 1,717 mm of precipitation per year, spread over about 200 rainy days.

Is it sunny in Lang Son?

Lang Son gets on average 7.1 hours of sunshine per day, roughly 2,592 hours per year over 1940-2025.

What is the biggest single-day snowfall in Lang Son?

The heaviest 24-hour snowfall measured in Lang Son between 1940 and 2025 was 24 January 2016, with 1.0 cm.

Are there tropical nights in Lang Son?

Yes: Lang Son has on average 185 tropical nights per year (temperature staying above 20 °C), over 1940-2025.

What was the most extreme apparent temperature in Lang Son?

In Lang Son, between 1940 and 2025, the highest apparent temperature reached 45.3 °C on 16 May 2013, and the lowest was -4.4 °C on 24 January 2016.

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