Cát Bà weather in May

In May, Cát Bà sees average daytime highs of 28°C and overnight lows near 26°C, with 185 mm of rain across 15.5 wet days and about 13 hours of daylight. It is the 5th-warmest and 5th-wettest month of the year here.

Highs climb over the month, from about 27°C in the first days to 29°C by the end. The sky is clear or mostly clear about 21% of the time in May, and the air most often feels miserable.

Daylight stretches from about 12 h 42 min at the start of May to 13 h 12 min by month's end. Set against the rest of the year, May is Cát Bà's 6th-clearest and 7th-windiest month. For the whole year in context, see Cát Bà's year-round climate.

Daytime high
28°
5th warmest
Overnight low
26°
8th coldest
Rainfall
185 mm
15.5 wet days
Daylight
13 hours
5:19 AM – 6:18 PM
Cloud cover
69%
6th clearest
Wind
16 km/h
7th windiest
Solar energy
5.4 kWh/m²
Travel score
5.1
out of 10

Cát Bà is town in Vietnam.

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

Temperature in May

Average highAverage lowShaded bands: 10–90% of days

Highs climb over the month, from about 27°C in the first days to 29°C by the end.

A typical May day in Cát Bà reaches about 28°C in the afternoon and slips back to 26°C overnight — a 2°C spread between the day's warmth and the night's chill. On most days the high lands between 26°C and 30°C. Set against its neighbours, May runs about 4°C warmer than April and about 2°C cooler than June.

20°25°30°35°151015202531
Avg high (°C)Avg low (°C)
12725
22725
32725
42725
52725
62725
72725
82825
92825
102825
112825
122826
132826
142826
152826
162826
172826
182826
192926
202926
212926
222926
232926
242927
252927
262927
272927
282927
292927
302927
312927

How May really feels in Cát Bà

Once humidity and wind are folded in, May averages 19 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
19
heat index over the day's high
Days feeling ≤ C
0
wind chill below the day's low

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

Cát Bà weather by month

How May compares with the rest of the year at a glance. May is the 5th-warmest and 5th-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 May

ClearMostly clearPartly cloudyMostly cloudyOvercast

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

Beyond those clear spells, partly cloudy skies cover about 14% of May, with mostly cloudy or overcast conditions the remaining 65%. Skies tend to cloud over as the month goes on.

0%25%50%75%100%151015202531
Clearer (%)Cloudier (%)
14654
24654
34555
44654
54555
64555
74555
84456
94456
104357
114357
124258
133961
143961
153763
163664
173565
183367
193268
203169
212971
222773
232773
242674
252575
262476
272476
282377
292278
302179
312080

Chance of precipitation in May

Any precipitation

Cát Bà gets around 185 mm of rain over 15.5 wet days in May. The line is the day-by-day chance of measurable precipitation.

Day to day, the chance of measurable rain averages around 49% and peaks near 57% on the wettest days. The odds climb toward the end of the month.

0%20%40%60%151015202531
Rain chance (%)
137
239
340
441
543
644
745
846
947
1047
1148
1248
1349
1449
1549
1650
1750
1850
1951
2051
2152
2252
2353
2453
2554
2654
2755
2855
2956
3056
3157

Humidity in May

DryComfortableHumidMuggyOppressiveMiserable

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

By dew point, May lands in the miserable band about 66% of days. Sticky, muggy-or-worse air turns up on roughly 97% of them.

0%25%50%75%100%151015202531
Comfortable (%)Humid (%)Muggy (%)Oppressive (%)Miserable (%)
114124042
214123845
314113648
414113450
503113254
603103156
703102958
803102760
90392662
100292564
110292465
120292366
130292366
140292366
150292267
160282268
170282268
180282169
190282169
200282070
210272071
220272071
230271972
240261973
250261874
260161776
270151678
280151579
290141481
300141382
310131284

Wind in May

Winds average 16 km/h in May.

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

05101520151015202531
Wind speed (km/h)Feels
116light breeze
216light breeze
316light breeze
416light breeze
516light breeze
616light breeze
716light breeze
816light breeze
916light breeze
1016light breeze
1116light breeze
1216light breeze
1316light breeze
1416light breeze
1516light breeze
1616light breeze
1716light breeze
1816light breeze
1916light breeze
2016light breeze
2116light breeze
2216light breeze
2316light breeze
2416light breeze
2516light breeze
2616light breeze
2716light breeze
2816light breeze
2916light breeze
3016light breeze
3116light breeze

Sunrise & sunset in May

DaylightNight

Daylight runs from about 12 h 42 min at the start of May to 13 h 12 min by month's end. The lit band spans sunrise to sunset each day.

Days grow by about 30 minutes over May. Sunrise moves from 5:27 AM to 5:15 AM, and sunset from 6:11 PM to 6:24 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202531
Daylight (h)Sunrise (AM)Sunset (PM)
112.75:276:11
212.85:266:12
312.85:256:12
412.85:256:13
512.85:246:13
612.85:236:13
712.85:236:14
812.95:226:14
912.95:226:15
1012.95:216:15
1112.95:216:15
1212.95:206:16
1312.95:206:16
1413.05:196:17
1513.05:196:17
1613.05:196:18
1713.05:186:18
1813.05:186:18
1913.05:176:19
2013.05:176:19
2113.05:176:20
2213.15:166:20
2313.15:166:21
2413.15:166:21
2513.15:166:21
2613.15:156:22
2713.15:156:22
2813.15:156:23
2913.15:156:23
3013.15:156:23
3113.25:156:24

Solar energy in May

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in May, about 5.4 kWh/m² — the sunniest month for solar.

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 — May's 5.4 kWh/m² sits near the top of that range.

0246151015202531
Solar energy (kWh/m²)Level
15.5Bright
25.5Bright
35.5Bright
45.5Bright
55.5Bright
65.5Bright
75.5Bright
85.5Bright
95.5Bright
105.5Bright
115.5Bright
125.5Bright
135.4Bright
145.4Bright
155.4Bright
165.4Bright
175.4Bright
185.4Bright
195.4Bright
205.4Bright
215.4Bright
225.3Bright
235.3Bright
245.3Bright
255.3Bright
265.3Bright
275.3Bright
285.3Bright
295.3Bright
305.3Bright
315.3Bright
Planning a trip in May

Hazard calendar for Cát Bà

In seasonPeak

In May, Cát Bà sits inside its pacific typhoon and monsoon 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 May a good time to visit Cát Bà?

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

5.1
Sightseeing
8th-best month of the year
5.9
Beach & pool
4th-best month of the year

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

What to pack for Cát Bà in May

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

In May, Cát Bà sees daytime highs around 28°C and nights near 26°C. Pack light clothes and rain gear. Worth having: sun protection. About 16 days see rain.

light clothesrain gearsun protection

Sea temperature near Cát Bà in May

The nearest coast averages about 27°C in May — 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 May

LowModerateHighVery highExtreme

Clear-sky midday UV in May 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 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 May

GoodModeratePoorUnhealthyVery unhealthy

Average fine-particle pollution (PM2.5) through the year — so you can see where May 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
May 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).