Climate and average weather in Ha Long
In Ha Long, the summers are oppressive, hot, wet, and mostly cloudy and the winters are mild and mostly cloudy.
Over the course of the year, the temperature in Ha Long typically varies from 15°C to 31°C, and is rarely below 10°C or above 34°C. June is the hottest month of the year, while January is the coldest.
Based on the travel score, the best time of year to visit Ha Long for warm-weather activities is from late October to late April.
- Hottest
- Jun
- 31°
- Coldest
- Jan
- 15°
- Wettest
- Aug
- 381 mm
- Driest
- Feb
- 21 mm
- Rain / yr
- 1766 mm
- 171 wet days
- Daylight
- 10.7–13.3 h
- shortest–longest
- Elevation
- 8 m
- 21.0°N
- Clearest
- Oct
- 53% cloud
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.
Ha Long weather by month, at a glance
The whole year in one picture — sky, rain, humidity, temperature and travel score. Click any band to jump to its full chart.
Each stripe is one measure across the whole year, stacked so a single day reads top to bottom. The sky band runs overcast grey on top down to clear blue at the base — more blue means sunnier — followed by the rainfall curve, the humidity band, a temperature strip that tints each stretch of the year by how warm its average high is, and the travel-score line at the foot. Scan straight down any date to read that day across every measure at once; the score climbs highest around late October to late April.
Temperature through the year
Daily average highs and lows in Ha Long, from 1991–2020 of climate data. The shaded bands show the range most days fall in — 10th to 90th percentile.
The hot season lasts 5.7 months, from April 29 to October 19, with daily high temperatures above 28°C. The hottest month of the year in Ha Long is June, with an average high of 31°C and low of 27°C.
The cool season lasts 2.5 months, from December 15 to March 1, with daily high temperatures below 21°C. The coldest month of the year in Ha Long is January, with an average low of 15°C and high of 19°C.
Days typically run about 5°C warmer than nights year-round.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg high (°C) | 19 | 20 | 22 | 26 | 30 | 31 | 31 | 31 | 30 | 28 | 25 | 21 |
| Avg low (°C) | 15 | 16 | 18 | 22 | 25 | 27 | 27 | 26 | 25 | 23 | 19 | 16 |
| Avg high (°C) | Avg low (°C) | |
|---|---|---|
| Jan | 19 | 15 |
| Feb | 20 | 16 |
| Mar | 22 | 18 |
| Apr | 26 | 22 |
| May | 30 | 25 |
| Jun | 31 | 27 |
| Jul | 31 | 27 |
| Aug | 31 | 26 |
| Sep | 30 | 25 |
| Oct | 28 | 23 |
| Nov | 25 | 19 |
| Dec | 21 | 16 |
How hot and cold Ha Long really feels
The felt-temperature range through the year — heat index on the day's high (summer humidity), wind chill on the night's low (winter wind). The dashed lines are the plain thermometer; the gap is how much hotter or colder it really feels.
On the hottest afternoons, once humidity is folded in, Ha Long feels like about 40°C (around June 26). About 158 days a year carry some heat stress, and 65 of them tip into dangerous heat (feels-like above 39°C), peaking in June.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Feels-like high (°C) | 19 | 20 | 22 | 27 | 35 | 39 | 39 | 39 | 36 | 31 | 25 | 21 |
| Air high (°C) | 19 | 20 | 22 | 26 | 30 | 31 | 31 | 31 | 30 | 28 | 25 | 21 |
| Feels-like low (°C) | 14 | 16 | 18 | 22 | 25 | 27 | 27 | 26 | 25 | 23 | 19 | 16 |
| Air low (°C) | 15 | 16 | 18 | 22 | 25 | 27 | 27 | 26 | 25 | 23 | 19 | 16 |
| Feels-like high (°C) | Air high (°C) | Feels-like low (°C) | Air low (°C) | |
|---|---|---|---|---|
| Jan | 19 | 19 | 14 | 15 |
| Feb | 20 | 20 | 16 | 16 |
| Mar | 22 | 22 | 18 | 18 |
| Apr | 27 | 26 | 22 | 22 |
| May | 35 | 30 | 25 | 25 |
| Jun | 39 | 31 | 27 | 27 |
| Jul | 39 | 31 | 27 | 27 |
| Aug | 39 | 31 | 26 | 26 |
| Sep | 36 | 30 | 25 | 25 |
| Oct | 31 | 28 | 23 | 23 |
| Nov | 25 | 25 | 19 | 19 |
| Dec | 21 | 21 | 16 | 16 |
Average hourly temperature in Ha Long
A compact picture of the whole year, hour by hour: each column is a day, each row an hour, and the color is the modeled average temperature. Darker overlays mark night, lighter ones the civil-twilight hours around sunrise and sunset.
Read left to right for the day of the year and top to bottom for the hour of the day; the color is the modeled temperature, cool blues through to hot reds on the same scale as the other charts. A vertical slice is a single day's swing — coolest just before dawn, warmest in the mid-afternoon — while a horizontal slice follows one hour across the seasons. The darker overlay marks night and the lighter one the twilight around sunrise and sunset. Colors run warmest on June afternoons, near 31°C, and coldest before dawn in January, near 15°C.
Ha Long weather by month
Every month at a glance. Click a month for its detailed page.
| Month | High / Low (°C) | Rainfall (mm) | Wet days | Daylight (hours) | Travel score |
|---|---|---|---|---|---|
| Jan | 19° / 15° | 34 | 6.5 | 10.9 | 6.3 |
| Feb | 20° / 16° | 21 | 5.6 | 11.3 | 6.4 |
| Mar | 22° / 18° | 44 | 8.8 | 11.9 | 6.5 |
| Apr | 26° / 22° | 69 | 11.6 | 12.5 | 6.0 |
| May | 30° / 25° | 219 | 19.5 | 13 | 3.9 |
| Jun | 31° / 27° | 266 | 22.4 | 13.2 | 2.9 |
| Jul | 31° / 27° | 305 | 24.3 | 13.1 | 2.8 |
| Aug | 31° / 26° | 381 | 26.2 | 12.7 | 2.7 |
| Sep | 30° / 25° | 243 | 20 | 12.1 | 3.6 |
| Oct | 28° / 23° | 104 | 11.9 | 11.5 | 5.7 |
| Nov | 25° / 19° | 51 | 8.2 | 11 | 7.1 |
| Dec | 21° / 16° | 31 | 5.9 | 10.8 | 7.0 |
Chance of rain
How likely it is to rain on a typical day, and how that shifts across the wetter and drier seasons.
Ha Long gets about 1766 mm of precipitation a year. On a typical day the chance of rain is very wet, but that rises and falls sharply with the seasons.
The wetter season lasts 5.3 months, from around Apr 27 to Oct 3, peaking in August at about 86% chance on a given day. The drier stretch runs the rest of the year, bottoming out around Dec 20.
August is the wettest month by volume, with 381 mm over about 26 wet days; February is the driest, with 21 mm.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Rain on a day (%) | 21 | 20 | 28 | 40 | 62 | 74 | 79 | 84 | 66 | 38 | 27 | 20 |
| Rain days | 7 | 6 | 9 | 12 | 20 | 22 | 24 | 26 | 20 | 12 | 8 | 6 |
| Rain on a day (%) | Rain days | |
|---|---|---|
| Jan | 21 | 7 |
| Feb | 20 | 6 |
| Mar | 28 | 9 |
| Apr | 40 | 12 |
| May | 62 | 20 |
| Jun | 74 | 22 |
| Jul | 79 | 24 |
| Aug | 84 | 26 |
| Sep | 66 | 20 |
| Oct | 38 | 12 |
| Nov | 27 | 8 |
| Dec | 20 | 6 |
Monthly rainfall
Over a full year, Ha Long collects about 1766 mm of rain across 171 wet days — roughly 147 mm in an average month.
It doesn’t fall evenly. August is the wettest month with 381 mm, while February is the driest at just 21 mm. The three wettest months alone bring about 54% of the year’s total.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Rainfall (mm) | 34 | 21 | 44 | 69 | 219 | 266 | 305 | 381 | 243 | 104 | 51 | 31 |
| Rain days | 7 | 6 | 9 | 12 | 20 | 22 | 24 | 26 | 20 | 12 | 8 | 6 |
| Rainfall (mm) | Rain days | |
|---|---|---|
| Jan | 34 | 7 |
| Feb | 21 | 6 |
| Mar | 44 | 9 |
| Apr | 69 | 12 |
| May | 219 | 20 |
| Jun | 266 | 22 |
| Jul | 305 | 24 |
| Aug | 381 | 26 |
| Sep | 243 | 20 |
| Oct | 104 | 12 |
| Nov | 51 | 8 |
| Dec | 31 | 6 |
Clouds and sunshine
How often the daytime sky is clear, partly cloudy or overcast.
In Ha Long, the average share of the sky covered by clouds shows significant seasonal variation over the course of the year.
The clearer part of the year begins around September 11 and lasts for 3.8 months, ending around January 5. The clearest month is October, when the sky is clear, mostly clear, or partly cloudy 59% of the time on average.
The cloudier part of the year begins around May 15 and lasts for 3.9 months, ending around September 10. The cloudiest month is June, when it is overcast or mostly cloudy 88% of the time.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Clearer (%) | 26 | 23 | 19 | 27 | 27 | 12 | 16 | 19 | 36 | 59 | 56 | 41 |
| Cloudier (%) | 74 | 77 | 81 | 73 | 73 | 88 | 84 | 81 | 64 | 41 | 44 | 59 |
| Clearer (%) | Cloudier (%) | |
|---|---|---|
| Jan | 26 | 74 |
| Feb | 23 | 77 |
| Mar | 19 | 81 |
| Apr | 27 | 73 |
| May | 27 | 73 |
| Jun | 12 | 88 |
| Jul | 16 | 84 |
| Aug | 19 | 81 |
| Sep | 36 | 64 |
| Oct | 59 | 41 |
| Nov | 56 | 44 |
| Dec | 41 | 59 |
Daylight, sunrise and sunset
Hours of daylight through the year, with sunrise and sunset times.
The gold band is daylight — sunrise runs along its lower edge, sunset along the upper — so it widens toward summer and pinches toward winter, with night the dark area above and below. The longest day, around June 12, brings about 13 h 18 min of light; the shortest, around January 1, only 10 h 42 min — a swing of roughly 2 h 36 min.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Daylight (h) | 10.9 | 11.3 | 11.9 | 12.5 | 13.0 | 13.2 | 13.1 | 12.7 | 12.1 | 11.5 | 11.0 | 10.8 |
| Sunrise (AM) | 6:35 | 6:28 | 6:06 | 5:38 | 5:18 | 5:14 | 5:23 | 5:34 | 5:42 | 5:51 | 6:07 | 6:26 |
| Sunset (PM) | 5:27 | 5:45 | 5:57 | 6:06 | 6:18 | 6:30 | 6:32 | 6:17 | 5:50 | 5:22 | 5:07 | 5:10 |
| Daylight (h) | Sunrise (AM) | Sunset (PM) | |
|---|---|---|---|
| Jan | 10.9 | 6:35 | 5:27 |
| Feb | 11.3 | 6:28 | 5:45 |
| Mar | 11.9 | 6:06 | 5:57 |
| Apr | 12.5 | 5:38 | 6:06 |
| May | 13.0 | 5:18 | 6:18 |
| Jun | 13.2 | 5:14 | 6:30 |
| Jul | 13.1 | 5:23 | 6:32 |
| Aug | 12.7 | 5:34 | 6:17 |
| Sep | 12.1 | 5:42 | 5:50 |
| Oct | 11.5 | 5:51 | 5:22 |
| Nov | 11.0 | 6:07 | 5:07 |
| Dec | 10.8 | 6:26 | 5:10 |
Sunny days
How many genuinely sunny days each month brings — days the sky stays clear or mostly clear — banded into plain-language zones.
Ha Long averages about 6 sunny days a month — counting the days the sky stays clear or mostly clear — with a clear seasonal swing between 2 and 14 days.
The sunnier stretch runs 3.9 months, from around Sep 13 to Jan 8. The sunniest month is October, with roughly 12 sunny days (mixed).
The greyest month is June, down near 2 sunny days — about 83% fewer than the October peak.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Sunny days | 5 | 4 | 3 | 4 | 4 | 2 | 3 | 3 | 7 | 12 | 11 | 9 |
| Sky | Gloomy | Gloomy | Gloomy | Gloomy | Gloomy | Gloomy | Gloomy | Gloomy | Gloomy | Mixed | Mixed | Mixed |
| Sunny days | Sky | |
|---|---|---|
| Jan | 5 | Gloomy |
| Feb | 4 | Gloomy |
| Mar | 3 | Gloomy |
| Apr | 4 | Gloomy |
| May | 4 | Gloomy |
| Jun | 2 | Gloomy |
| Jul | 3 | Gloomy |
| Aug | 3 | Gloomy |
| Sep | 7 | Gloomy |
| Oct | 12 | Mixed |
| Nov | 11 | Mixed |
| Dec | 9 | Mixed |
Humidity comfort
Share of days at each humidity comfort level, based on the dew point — the measure that tracks how muggy it actually feels.
Humidity comfort is graded by the dew point — the temperature at which the air would be fully saturated — because it tracks how muggy it actually feels far better than relative humidity does. A low dew point feels dry and crisp; a high one feels sticky and oppressive no matter the reading on a humidity gauge.
In Ha Long, how humid it feels changes dramatically over the year.
The more humid part of the year lasts 7.2 months, from around March 23 to October 28. The muggiest month is May, when the air feels humid, muggy or worse about 99% of the time.
The most comfortable stretch runs from around October 29 to March 22, and December is the most comfortable month — the air is dry or comfortable 65% of the time.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Dry (%) | 47 | 34 | 14 | 3 | 0 | 0 | 0 | 0 | 0 | 3 | 19 | 44 |
| Comfortable (%) | 20 | 20 | 14 | 5 | 1 | 0 | 0 | 0 | 0 | 6 | 17 | 21 |
| Humid (%) | 21 | 23 | 23 | 13 | 3 | 0 | 0 | 0 | 3 | 15 | 21 | 19 |
| Muggy (%) | 11 | 20 | 34 | 22 | 11 | 1 | 0 | 0 | 9 | 26 | 21 | 12 |
| Oppressive (%) | 1 | 3 | 15 | 47 | 28 | 6 | 2 | 4 | 25 | 37 | 20 | 4 |
| Miserable (%) | 0 | 0 | 0 | 10 | 58 | 92 | 98 | 96 | 63 | 13 | 2 | 0 |
| Dry (%) | Comfortable (%) | Humid (%) | Muggy (%) | Oppressive (%) | Miserable (%) | |
|---|---|---|---|---|---|---|
| Jan | 47 | 20 | 21 | 11 | 1 | 0 |
| Feb | 34 | 20 | 23 | 20 | 3 | 0 |
| Mar | 14 | 14 | 23 | 34 | 15 | 0 |
| Apr | 3 | 5 | 13 | 22 | 47 | 10 |
| May | 0 | 1 | 3 | 11 | 28 | 58 |
| Jun | 0 | 0 | 0 | 1 | 6 | 92 |
| Jul | 0 | 0 | 0 | 0 | 2 | 98 |
| Aug | 0 | 0 | 0 | 0 | 4 | 96 |
| Sep | 0 | 0 | 3 | 9 | 25 | 63 |
| Oct | 3 | 6 | 15 | 26 | 37 | 13 |
| Nov | 19 | 17 | 21 | 21 | 20 | 2 |
| Dec | 44 | 21 | 19 | 12 | 4 | 0 |
Wind
Average wind speed through the year, banded into plain-language speed zones so a number reads as 'breezy' or 'calm' without knowing the scale.
This is the average sustained wind speed at the standard 10 metres above open ground — the steady flow a weather station reports, not the sharper gusts that come and go, which can run half again as fast. It's the number that says whether a place is generally breezy or calm.
Across the year, average wind speed in Ha Long is typically calm, near 10 km/h, and varies little with the seasons.
The windier part of the year lasts 4.2 months, from around Mar 21 to Jul 25. The windiest month is July, averaging about 11 km/h (calm).
The calmer part of the year runs from around Jul 26 to Oct 6, with August the calmest month at about 9 km/h.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Wind speed (km/h) | 10 | 10 | 10 | 11 | 11 | 11 | 11 | 9 | 9 | 11 | 11 | 11 |
| Feels | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm |
| Wind speed (km/h) | Feels | |
|---|---|---|
| Jan | 10 | calm |
| Feb | 10 | calm |
| Mar | 10 | calm |
| Apr | 11 | calm |
| May | 11 | calm |
| Jun | 11 | calm |
| Jul | 11 | calm |
| Aug | 9 | calm |
| Sep | 9 | calm |
| Oct | 11 | calm |
| Nov | 11 | calm |
| Dec | 11 | calm |
Hazard calendar for Ha Long
When the seasonal hazards worth planning around — the rainy season, tropical-cyclone risk and dust haze — are active through the year.
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.
Best time to visit Ha Long
To characterize how pleasant the weather is in Ha Long throughout the year, we compute two travel scores — one for general sightseeing, one for beach and pool weather.
Around mid April, Ha Long is still near the tail of its best-weather window — great conditions with the peak-season crowds already thinning.
Inferred from the travel-score curve; month-by-month visitor numbers are a planned addition.
The travel score favors clear, rainless days with daytime highs between 18°C and 28°C. Based on this score, the best time of year to visit Ha Long for general outdoor tourist activities is from late October to late April, with a peak score in the last week of November.
The travel score (filled area), and its constituents: the temperature score (red line), the cloud cover score (blue line), and the precipitation score (green line).
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Travel score (0–10) | 6.3 | 6.5 | 6.5 | 6.0 | 4.0 | 2.9 | 2.8 | 2.8 | 3.7 | 5.7 | 7.1 | 7.0 |
| Rating | good | good | good | good | fair | poor | poor | poor | fair | good | good | good |
| Travel score (0–10) | Rating | |
|---|---|---|
| Jan | 6.3 | good |
| Feb | 6.5 | good |
| Mar | 6.5 | good |
| Apr | 6.0 | good |
| May | 4.0 | fair |
| Jun | 2.9 | poor |
| Jul | 2.8 | poor |
| Aug | 2.8 | poor |
| Sep | 3.7 | fair |
| Oct | 5.7 | good |
| Nov | 7.1 | good |
| Dec | 7.0 | good |
The beach/pool score favors clear, rainless days with daytime highs between 24°C and 34°C. Based on this score, the best times of year to visit Ha Long for hot-weather activities run from early April to early May and again from late September to late November, with a peak score in the last week of October.
The beach/pool score (filled area), and its constituents: the temperature score (red line), the cloud cover score (blue line), and the precipitation score (green line).
What to pack for Ha Long, by month
Month by month, what's worth putting in the bag — from the temperature range, rain chance, sun and wind. Tap a month for a quick packing note.
For a warm-season trip around June (highs near 31°C), the essentials are light clothes, rain gear and sun protection. In the cold season around January (highs near 19°C), pack a light layer.
In June, Ha Long sees daytime highs around 31°C and nights near 27°C. Pack light clothes and rain gear. Worth having: sun protection. About 22 days see rain.
Sea temperature near Ha Long
Average ocean temperature at the nearest coast, month by month, banded into swim-comfort zones — the other half of the beach question.
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.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Sea temperature (°C) | 20 | 19 | 20 | 23 | 27 | 29 | 29 | 30 | 29 | 28 | 25 | 22 |
| Comfort | Cool | Cool | Refreshing | Refreshing | Warm | Tropical | Tropical | Tropical | Tropical | Warm | Warm | Refreshing |
| Sea temperature (°C) | Comfort | |
|---|---|---|
| Jan | 20 | Cool |
| Feb | 19 | Cool |
| Mar | 20 | Refreshing |
| Apr | 23 | Refreshing |
| May | 27 | Warm |
| Jun | 29 | Tropical |
| Jul | 29 | Tropical |
| Aug | 30 | Tropical |
| Sep | 29 | Tropical |
| Oct | 28 | Warm |
| Nov | 25 | Warm |
| Dec | 22 | Refreshing |
UV index (midday) in Ha Long by month
Clear-sky midday UV index through the year, shaded by the WHO exposure levels — how much sun protection each month calls for.
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.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| UV index (midday) | 7 | 8 | 9 | 8 | 10 | 12 | 12 | 9 | 9 | 9 | 7 | 6 |
| Level | High | Very high | Very high | Very high | Extreme | Extreme | Extreme | Very high | Very high | Very high | High | High |
| UV index (midday) | Level | |
|---|---|---|
| Jan | 7 | High |
| Feb | 8 | Very high |
| Mar | 9 | Very high |
| Apr | 8 | Very high |
| May | 10 | Extreme |
| Jun | 12 | Extreme |
| Jul | 12 | Extreme |
| Aug | 9 | Very high |
| Sep | 9 | Very high |
| Oct | 9 | Very high |
| Nov | 7 | High |
| Dec | 6 | High |
Average hourly UV index in Ha Long
Modeled clear-sky UV for every hour of every day — when in the day sun protection actually matters.
The whole year hour by hour: each column is a day, each row an hour, and the color is the modeled clear-sky UV index — the midday peak scaled down as the sun sits lower in the sky. Darker overlays mark night, lighter ones the civil-twilight hours around sunrise and sunset.
UV falls off far faster than brightness as the sun drops, so even in July the burn window is concentrated in the middle of the day: about 8.5 hours a day reach index 3 (protection recommended), and 6.5 hours reach 6 or more. Mornings and late afternoons stay comparatively gentle year round.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| UV ≥ 3 (h/day) | 6 | 6.5 | 7 | 7 | 8 | 8.5 | 8.5 | 7.5 | 7.5 | 7 | 6 | 5.5 |
| UV ≥ 6 (h/day) | 2.5 | 4 | 4.5 | 4 | 5.5 | 6 | 6.5 | 4.5 | 5 | 4.5 | 2.5 | 1.5 |
| UV ≥ 3 (h/day) | UV ≥ 6 (h/day) | |
|---|---|---|
| Jan | 6 | 2.5 |
| Feb | 6.5 | 4 |
| Mar | 7 | 4.5 |
| Apr | 7 | 4 |
| May | 8 | 5.5 |
| Jun | 8.5 | 6 |
| Jul | 8.5 | 6.5 |
| Aug | 7.5 | 4.5 |
| Sep | 7.5 | 5 |
| Oct | 7 | 4.5 |
| Nov | 6 | 2.5 |
| Dec | 5.5 | 1.5 |
Air quality in Ha Long by month
Average fine-particle pollution (PM2.5) through the year — so you can see which months the air is worst, not just the yearly 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).
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| PM2.5 (µg/m³) | 42 | 42 | 41 | 40 | 26 | 19 | 16 | 18 | 21 | 27 | 29 | 39 |
| Level | Poor | Poor | Poor | Poor | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate | Poor |
| PM2.5 (µg/m³) | Level | |
|---|---|---|
| Jan | 42 | Poor |
| Feb | 42 | Poor |
| Mar | 41 | Poor |
| Apr | 40 | Poor |
| May | 26 | Moderate |
| Jun | 19 | Moderate |
| Jul | 16 | Moderate |
| Aug | 18 | Moderate |
| Sep | 21 | Moderate |
| Oct | 27 | Moderate |
| Nov | 29 | Moderate |
| Dec | 39 | Poor |
Growing season
Ha Long is frost-free year round — even the coldest nights rarely reach freezing, so there is no start or end to the growing season.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Frost-free chance (%) | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 100 |
| Frost nights | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
| Frost-free chance (%) | Frost nights | |
|---|---|---|
| Jan | 100 | 0 |
| Feb | 100 | 0 |
| Mar | 100 | 0 |
| Apr | 100 | 0 |
| May | 100 | 0 |
| Jun | 100 | 0 |
| Jul | 100 | 0 |
| Aug | 100 | 0 |
| Sep | 100 | 0 |
| Oct | 100 | 0 |
| Nov | 100 | 0 |
| Dec | 100 | 0 |
Growing degree days
Growing degree days tally heat above 10°C: each day adds however many degrees its average temperature runs over that threshold, and cold days add nothing. Ha Long banks about 5,064 degree days a year, and the running total — which growers use to time plantings and predict maturity — climbs fastest around June.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Growing degree days (°C·days) | 209 | 220 | 320 | 420 | 533 | 567 | 586 | 572 | 527 | 481 | 367 | 261 |
| Growing degree days (°C·days) | |
|---|---|
| Jan | 209 |
| Feb | 220 |
| Mar | 320 |
| Apr | 420 |
| May | 533 |
| Jun | 567 |
| Jul | 586 |
| Aug | 572 |
| Sep | 527 |
| Oct | 481 |
| Nov | 367 |
| Dec | 261 |
Solar energy
Average daily shortwave solar energy reaching the ground, banded into brightness zones so the number means something at a glance.
Solar energy is how much sunlight actually reaches the ground each day, measured in kilowatt-hours per square metre (kWh/m²) — the combined effect of how long the sun is up, how high it climbs, and how much cloud gets in the way. It's the raw fuel a solar panel has to work with: for scale, 1 kWh/m² a day is dim and wintry, while 7+ is desert-bright.
Ha Long receives about 4.0 kWh/m² a day of solar energy on average — bright — with a clear seasonal swing between 2.6 and 5.1 kWh/m².
The brighter stretch of the year lasts 6.9 months, from around Apr 5 to Oct 31. The brightest month is May, averaging about 5.1 kWh/m² (bright).
The dimmest month is January, down near 2.6 kWh/m² — roughly 48% less than the May peak.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Solar energy (kWh/m²) | 2.6 | 2.9 | 3.5 | 4.6 | 5.1 | 5.0 | 5.0 | 4.6 | 4.5 | 4.4 | 3.5 | 2.9 |
| Level | Moderate | Moderate | Moderate | Bright | Bright | Bright | Bright | Bright | Bright | Bright | Moderate | Moderate |
| Solar energy (kWh/m²) | Level | |
|---|---|---|
| Jan | 2.6 | Moderate |
| Feb | 2.9 | Moderate |
| Mar | 3.5 | Moderate |
| Apr | 4.6 | Bright |
| May | 5.1 | Bright |
| Jun | 5.0 | Bright |
| Jul | 5.0 | Bright |
| Aug | 4.6 | Bright |
| Sep | 4.5 | Bright |
| Oct | 4.4 | Bright |
| Nov | 3.5 | Moderate |
| Dec | 2.9 | Moderate |
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.
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
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).