Similans Weather Forecast
17th - 23rd August 2026
Forecast data supplied by MET NorwayThai Meteorological Department
Does a rain symbol mean a washout?
NO. A rain icon can represent a passing tropical shower. For the long mainland crossing, wind, swell and the operator’s live sea assessment matter at least as much as rainfall probability.
Yearly forecast
Monthly rainfall
Average sunshine
Average temperature
Similan Islands weather month by month
These model-based 2016–2025 island averages show the usual weather pattern around the Similan Islands. The marine park normally opens from 15 October to 15 May and closes from 16 May to 14 October; always check the live forecast and the operator’s final crossing assessment.
What is the Similan Islands weather like in January?
January sits in the Similan visitor season and is normally bright and settled, averaging 27.2°C, about 10.5 sunshine hours a day and 53 mm of rain. Crossings are often more comfortable, making this a popular month for snorkelling and diving.
What is the Similan Islands weather like in February?
February is usually the driest Similan month, averaging 27.6°C, around 11.1 sunshine hours a day and just 28 mm of rain. The park is open and sea conditions are often among the season’s most settled, subject to the daily marine forecast.
What is the Similan Islands weather like in March?
March remains very sunny and becomes warmer, averaging 28.2°C, 11.1 sunshine hours a day and about 45 mm of rain. Most scheduled speedboat, snorkelling and diving trips operate normally when the live sea assessment is suitable.
What is the Similan Islands weather like in April?
April is typically hot and bright, averaging 28.6°C, around 10.7 sunshine hours a day and 107 mm of rain. The park remains open, though humidity and the chance of a short tropical shower increase later in the month.
What is the Similan Islands weather like in May?
May averages 28.5°C, about 8.9 sunshine hours a day and 262 mm of rain. Trips can operate through 15 May when conditions allow; the park normally closes from 16 May as the southwest-monsoon period begins.
What is the Similan Islands weather like in June?
June averages 28.2°C, around 8.8 sunshine hours a day and 216 mm of rain. The Similan marine park is normally closed, and the long open-sea crossing is more exposed to southwest-monsoon wind and waves.
What is the Similan Islands weather like in July?
July remains warm at about 28°C, with 8.7 sunshine hours a day and around 192 mm of rain. The marine park stays closed for conservation and because offshore sea conditions are less dependable for regular visitor crossings.
What is the Similan Islands weather like in August?
August averages 27.8°C, approximately 8.7 sunshine hours a day and 219 mm of rain. This is within the annual closure, when wind, swell and rougher mainland-to-island conditions are more common.
What is the Similan Islands weather like in September?
September averages 27.4°C, around 8 sunshine hours a day and 278 mm of rain. The park remains closed and southwest-monsoon conditions can make the exposed crossing unsuitable for normal visitor operations.
What is the Similan Islands weather like in October?
October is an opening-transition month, averaging 27.2°C, about 8.1 sunshine hours a day and 303 mm of rain. The park normally reopens on 15 October, but the first weeks can still be wet, windy or rough, so flexible planning matters.
What is the Similan Islands weather like in November?
November usually becomes brighter and more settled, averaging 27.4°C, 8.7 sunshine hours a day and around 198 mm of rain. The park is open; occasional lively crossings remain possible early in the month before the calmer season becomes established.
What is the Similan Islands weather like in December?
December is normally bright and comfortable, averaging 27.3°C, around 9.8 sunshine hours a day and 86 mm of rain. This is a popular visitor-season month, with most scheduled trips operating when the daily marine forecast is suitable.
Similan Islands Weather FAQ
When are the Similan Islands open?
The national marine park normally opens from 15 October to 15 May and closes from 16 May to 14 October. Always check the current park announcement and trip schedule before booking.
What is the best month to visit the Similan Islands?
January to March usually offers the brightest weather and most settled seas. December and April are also popular, while October and early November can be more changeable.
Are Similan speedboat crossings rough?
They can be. The islands are a long way offshore, so even an operating trip may feel lively when there is swell. The operator uses the current marine forecast and live conditions to make the final decision.
Does rain cancel a Similan Islands trip?
Not by itself. Wind, wave height, swell and official warnings matter more than a rain icon alone. Unsafe conditions can lead to a delay, route change, rescheduling or cancellation.
Is October a good time for the Similan Islands?
The park normally opens on 15 October, but the first two or three weeks can still be unsettled. Later November through April is generally more dependable for long crossings.
Why are the Similan Islands closed in the green season?
The closure protects the marine environment and coincides with the southwest monsoon, when the exposed mainland crossing is more frequently affected by rough seas.
Can Phuket and the Similan Islands have different weather?
Yes. The Similans are far offshore, so sunshine, rain, wind and waves can differ materially from Phuket or the Khao Lak mainland.
How accurate is the seven-day Similan forecast?
It is useful for planning trends. Recheck the final 24–48 hours and follow the operator’s live assessment because offshore forecasts and sea conditions can change.
What happens if a Similan trip cannot operate?
The available alternative, rescheduling or refund arrangement depends on the operator and booking terms. Your booking confirmation should state the applicable process.