Official warning
Official notice, KTTV Trung Bộ, 16:12, Oct 27: «TIN DỰ BÁO MƯA DÔNG, LỐC XOÁY VÀ GIÓ GIẬT MẠNH TRÊN BIỂN TỈNH KHÁNH HÒA» (quoted in Vietnamese exactly as published; we do not translate official warnings) Source
When the sea is rough, ask the tour operator before you go whether the boat will sail.
Island trip window: 7 days
Next good day for the islands: Tuesday Oct 27 (7/10). Also good: Sun Nov 1
- TueOct 277/10goodTuesday Oct 27: 7/10 - good conditions; offshore waves up to 0.6 m, gusts up to 33 km/h, rain 3.8 mm
- WedOct 286/10so-soWednesday Oct 28: 6/10 - caution; offshore waves up to 0.5 m, gusts up to 44 km/h, rain 1.1 mm
- ThuOct 294/10poorThursday Oct 29: 4/10 - difficult conditions; offshore waves up to 0.6 m, gusts up to 36 km/h, rain 30.3 mm
- FriOct 307/10so-soFriday Oct 30: 7/10 - caution; offshore waves up to 0.7 m, gusts up to 35 km/h, rain 5.8 mm
- SatOct 314/10so-soSaturday Oct 31: 4/10 - caution; offshore waves up to 0.6 m, gusts up to 44 km/h, rain 12.1 mm
- SunNov 18/10goodSunday Nov 1: 8/10 - good conditions; offshore waves up to 0.7 m, gusts up to 28 km/h, rain 2.4 mm
- MonNov 26/10so-soMonday Nov 2: 6/10 - caution; offshore waves up to 0.6 m, gusts up to 35 km/h, rain 10.9 mm
Whether boats sail is decided by the port and the tour operator - ask them before you book. A low score means a rough sea: tours are more likely to be cancelled or to cause seasickness.
A reference index, not an official forecast. Official warnings: Vietnam National Centre for Hydro-Meteorological Forecasting (nchmf.gov.vn).
Open-Meteo model (Marine + Forecast), updated 19:00 (Nha Trang time)
Day by day
- Tuesday Oct 27: 7/10 - good conditions; offshore waves up to 0.6 m, gusts up to 33 km/h, rain 3.8 mm
- Wednesday Oct 28: 6/10 - caution; offshore waves up to 0.5 m, gusts up to 44 km/h, rain 1.1 mm
- Thursday Oct 29: 4/10 - difficult conditions; offshore waves up to 0.6 m, gusts up to 36 km/h, rain 30.3 mm
- Friday Oct 30: 7/10 - caution; offshore waves up to 0.7 m, gusts up to 35 km/h, rain 5.8 mm
- Saturday Oct 31: 4/10 - caution; offshore waves up to 0.6 m, gusts up to 44 km/h, rain 12.1 mm
- Sunday Nov 1: 8/10 - good conditions; offshore waves up to 0.7 m, gusts up to 28 km/h, rain 2.4 mm
- Monday Nov 2: 6/10 - caution; offshore waves up to 0.6 m, gusts up to 35 km/h, rain 10.9 mm
7 or more: good4-7: so-sobelow 4: poor
How the score is worked out
The score from 0 to 10 uses three numbers from the Open-Meteo model: the highest wave around the islands, wind gusts and the forecast rain for the day in millimetres (the chance of rain is close to 100% almost every day in the rainy season, so it cannot rank days). The bigger the waves, wind and rain, the lower the score. A low score means a rough sea: tours are more likely to be cancelled or to cause seasickness. With waves of 1.5 m or more, or gusts of 50 km/h or more, the score never goes above 2.
Where the boats usually go
The score applies to the area of the islands in Nha Trang bay: Hon Mun, Hon Tam, Hon Mot.
By season
October: calm sea (waves under 1 m) on 88% of days, 5 mm or more of rain on 31% of days.
The roughest months (calm sea on fewer than 60% of days): January, February, November, December.
This is the north-east monsoon season: tours are more often cancelled or cause seasickness.
The rainiest months (5 mm or more of rain on over 25% of days): October, November.
Statistics from past years, not a forecast.
Jellyfish season in the bay usually runs from May to August. It is mostly fire jellyfish or loose tentacle fragments carried by currents, so there is no fixed spot.
Source: VnExpress, 07/08/2026, checked 2026-10-19
Frequently asked questions
Which day is best for an island trip from Nha Trang?
By the reference score, the next good day is Tuesday Oct 27 (7/10); also good: Sun Nov 1. Today scores 7/10. This is a reference index, not an official forecast. Official warnings: Vietnam National Centre for Hydro-Meteorological Forecasting (nchmf.gov.vn).
In what weather are island trips cancelled?
Whether boats sail is decided by the port and the tour operator, not by this site. As a guide, our score never goes above 2 when waves reach 1.5 m or gusts reach 50 km/h - on such days trips may be cancelled. Ask the operator the evening before.
Where does the wave data for the islands come from?
From the Open-Meteo Marine model (wave height) and Open-Meteo Forecast (wind gusts and chance of rain), at a point near the islands of Nha Trang bay. The data is refreshed several times a day. It is a model, not a measurement from a boat, so the real waves may differ.