Cát Bà weather in December

In December, Cát Bà sees average daytime highs of 21°C and overnight lows near 18°C, with 39 mm of rain across 6.3 wet days and about 10.8 hours of daylight. It is the 10th-warmest and 11th-wettest month of the year here.

Highs ease over the month, from about 22°C in the first days to 20°C by the end. The sky is clear or mostly clear about 31% of the time in December, and the air most often feels dry.

Daylight stretches from about 10 h 48 min at the start of December to 10 h 48 min by month's end. Set against the rest of the year, December is Cát Bà's 3rd-clearest and 3rd-windiest month. For the whole year in context, see Cát Bà's year-round climate.

Daytime high
21°
10th warmest
Overnight low
18°
3rd coldest
Rainfall
39 mm
6.3 wet days
Daylight
10 h 42 min
6:26 AM – 5:10 PM
Cloud cover
60%
3rd clearest
Wind
17 km/h
3rd windiest
Solar energy
2.96 kWh/m²
Travel score
6.9
out of 10

Cát Bà is town in Vietnam.

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

Temperature in December

Average highAverage lowShaded bands: 10–90% of days

Highs ease over the month, from about 22°C in the first days to 20°C by the end.

A typical December day in Cát Bà reaches about 21°C in the afternoon and slips back to 18°C overnight — a 3°C spread between the day's warmth and the night's chill. On most days the high lands between 17°C and 23°C. Set against its neighbours, December runs about 4°C cooler than November and about 2°C warmer than January.

10°15°20°25°151015202531
Avg high (°C)Avg low (°C)
12220
22219
32219
42219
52219
62219
72219
82119
92118
102118
112118
122118
132118
142118
152118
162118
172018
182017
192017
202017
212017
222017
232017
242017
252017
262017
272017
282017
292017
302017
311917

How December really feels in Cát Bà

Once humidity and wind are folded in, December averages 0 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
0
heat index over the day's high
Days feeling ≤ C
0
wind chill below the day's low

December sits comfortably in between — no days that feel dangerously hot or drop to a hard freeze once humidity and wind are folded in.

Cát Bà weather by month

How December compares with the rest of the year at a glance. December is the 10th-warmest and 11th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°C)Rainfall (mm)Wet daysDaylight (hours)Travel score
Jan19° / 16°407.610.96.2
Feb19° / 17°235.711.36.4
Mar21° / 19°407.611.96.6
Apr25° / 23°527.712.57.0
May28° / 26°18515.5135.1
Jun30° / 28°21517.813.23.7
Jul30° / 28°30319.813.13.6
Aug30° / 27°3992412.73.3
Sep29° / 26°3052012.14.0
Oct28° / 25°13411.611.56.2
Nov24° / 21°568.4117.2
Dec21° / 18°396.310.86.9

Cloud cover in December

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 31% of the time in December.

Beyond those clear spells, partly cloudy skies cover about 15% of December, with mostly cloudy or overcast conditions the remaining 55%.

0%25%50%75%100%151015202531
Clearer (%)Cloudier (%)
15347
25149
35050
44951
54852
64753
74753
84555
94555
104456
114357
124357
134258
144357
154456
164456
174555
184555
194555
204555
214654
224654
234654
244654
254654
264654
274654
284456
294456
304357
314258

Chance of precipitation in December

Any precipitation

Cát Bà gets around 39 mm of rain over 6.3 wet days in December. The line is the day-by-day chance of measurable precipitation.

Day to day, the chance of measurable rain averages around 21% and peaks near 24% on the wettest days.

0%10%20%30%151015202531
Rain chance (%)
124
223
323
422
522
621
721
821
921
1021
1120
1220
1320
1420
1520
1620
1720
1820
1920
2020
2120
2220
2320
2420
2520
2621
2721
2822
2922
3023
3123

Humidity in December

DryComfortableHumidMuggyOppressiveMiserable

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

By dew point, December lands in the dry band about 38% of days. Sticky, muggy-or-worse air turns up on roughly 21% of them.

0%25%50%75%100%151015202531
Dry (%)Comfortable (%)Humid (%)Muggy (%)Oppressive (%)Miserable (%)
125212221111
226212221101
327212220101
42821221990
52922211980
63122211880
73222211870
83322211770
93422211760
103621211760
113721201650
123820201650
133920201650
144020191650
154119191650
164119191640
174219191640
184218191640
194318191540
204318201540
214318201440
224319211430
234319211330
244319221330
254319231320
264220231320
274120241320
284020251310
294020251410
303920261410
313920261510

Wind in December

Winds average 17 km/h in December.

Across December, daily wind ranges from about 16 km/h on the calmest days to 17 km/h at its breeziest. It stays fairly steady from day to day.

05101520151015202531
Wind speed (km/h)Feels
117light breeze
217light breeze
317light breeze
417light breeze
517light breeze
617light breeze
717light breeze
817light breeze
917light breeze
1017light breeze
1117light breeze
1217light breeze
1317light breeze
1417light breeze
1517light breeze
1617light breeze
1717light breeze
1817light breeze
1917light breeze
2017light breeze
2117light breeze
2217light breeze
2317light breeze
2417light breeze
2517light breeze
2617light breeze
2716light breeze
2816light breeze
2916light breeze
3016light breeze
3116light breeze

Sunrise & sunset in December

DaylightNight

Daylight runs from about 10 h 48 min at the start of December to 10 h 48 min by month's end. The lit band spans sunrise to sunset each day.

Days grow by about 0 minutes over December. Sunrise moves from 6:17 AM to 6:32 AM, and sunset from 5:07 PM to 5:18 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202531
Daylight (h)Sunrise (AM)Sunset (PM)
110.86:175:07
210.86:175:07
310.86:185:07
410.86:185:07
510.86:195:07
610.86:205:07
710.86:205:08
810.86:215:08
910.86:225:08
1010.86:225:08
1110.86:235:09
1210.86:235:09
1310.86:245:09
1410.86:245:10
1510.86:255:10
1610.76:265:10
1710.76:265:11
1810.76:275:11
1910.76:275:12
2010.76:285:12
2110.76:285:13
2210.76:295:13
2310.76:295:13
2410.76:295:14
2510.76:305:14
2610.76:305:15
2710.76:315:16
2810.76:315:16
2910.86:325:17
3010.86:325:17
3110.86:325:18

Solar energy in December

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in December, about 2.96 kWh/m².

For context, solar energy here swings from a low near 2.74 kWh/m² to a high of 5.4 kWh/m² in May across the year — December's 2.96 kWh/m² sits near the bottom.

01234151015202531
Solar energy (kWh/m²)Level
13.1Moderate
23.1Moderate
33.1Moderate
43.1Moderate
53.0Moderate
63.0Moderate
73.0Moderate
83.0Moderate
93.0Moderate
102.9Moderate
112.9Moderate
122.9Moderate
132.9Moderate
142.9Moderate
152.9Moderate
162.9Moderate
172.9Moderate
182.9Moderate
193.0Moderate
203.0Moderate
213.0Moderate
223.0Moderate
233.0Moderate
243.0Moderate
253.0Moderate
263.0Moderate
272.9Moderate
282.9Moderate
292.9Moderate
302.9Moderate
312.9Moderate
Planning a trip in December

Hazard calendar for Cát Bà

In seasonPeak

In December, Cát Bà sits inside its pacific typhoon season. The full year is below, with each hazard's peak months called out.

Cát Bà sits in the Pacific typhoon belt; the season peaks July–October.

Cát Bà'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 December a good time to visit Cát Bà?

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

6.9
Sightseeing
3rd-best month of the year
4.0
Beach & pool
10th-best month of the year

December is a reasonable time to visit Cát Bà for sightseeing.

What to pack for Cát Bà in December

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

In December, Cát Bà sees daytime highs around 21°C and nights near 18°C. Little to plan around — just the basics. About 6 days see rain.

Sea temperature near Cát Bà in December

The nearest coast averages about 22°C in December — the other half of the beach question. The full-year curve and swim-comfort zones are below.

The sea at the nearest coast (about 14 km away) is warmest in August at about 30°C and coldest in February near 20°C.

It's comfortable for a long swim from Mar 6 to Jan 18 — about 10.5 months when the water holds above 20°C.

20°25°30°JanFebMarAprMayJunJulAugSepOctNovDeccoolrefreshingwarmtropicalcomfortable to swim
Sea temperature (°C)Comfort
Jan20Refreshing
Feb20Cool
Mar20Refreshing
Apr23Refreshing
May27Warm
Jun29Tropical
Jul30Tropical
Aug30Tropical
Sep29Tropical
Oct28Warm
Nov25Warm
Dec22Refreshing

UV index in Cát Bà in December

LowModerateHighVery highExtreme

Clear-sky midday UV in December peaks around 6 — enough to warrant sun protection. The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in Cát Bà 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 Cát Bà in December

GoodModeratePoorUnhealthyVery unhealthy

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

Air quality in Cát Bà 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 Cát Bà?

Cát Bà sits at 20.7°N, 107.0°E, 24 m above sea level, in Vietnam. The nearest listed city is Ha Long, 25 km away.

Topography around Cát Bà

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

Within 3 km, the terrain around Cát Bà has only modest variations in elevation — a maximum elevation change of 205 m around an average of 22 m above sea level; within 16 km, significant variations in elevation — a maximum elevation change of 299 m; within 80 km, large variations in elevation — a maximum elevation change of 1,180 m.

The land around Cát Bà is covered by water (58%) and trees (36%) within 3 km, water (80%) within 16 km, and water (51%) and trees (29%) within 80 km.

3 km
205 m
16 km
299 m
80 km
1,180 m
treesgrasslandcroplandartificial surfacesbare terrainwatermangroves
December weather nearby: Ha Long 25 km · Đố Sơn 27 km · Cẩm Phả 39 km · Haiphong 41 km · Cẩm Phả Mines 41 km · Thành Phố Uông Bí 45 km · Kiến An 45 km · Thị Trấn Mạo Khê 60 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 Cát Bà (20.7278°, 107.0482°, elevation 24 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).