When to go
The Best Time to Visit Koh Samui
Month-by-month climate data for Koh Samui, Thailand — daily highs and lows, rain days, and an honest verdict for every month of the year.
Timing is the first real decision when planning Koh Samui— it drives crowds, prices and what's actually open. Here's how the year breaks down so you can pick dates that fit the trip you're building, not just the weather.
December–April. The Gulf's dry season (different from Phuket's!) — Samui's wettest months are October–November, when the Andaman side is drying out.
Warmest in Koh Samui: Apr (29°C / 84°F) · Coolest: Dec (25°C / 77°F) · Wettest: Oct (~27 rain days)
Daily highs / lows in °C · bars show rain days per month · ERA5 climate normals (2020–2024)
Koh Samui climate, month by month
January
26° / 22°C
~17 rain days
Good
February
26° / 22°C
~16 rain days
Good
March
28° / 23°C
~11 rain days
Excellent
April
29° / 24°C
~15 rain days
Good
May
29° / 24°C
~18 rain days
Good
June
29° / 24°C
~17 rain days
Good
July
28° / 23°C
~22 rain days
Good
August
29° / 23°C
~20 rain days
Good
September
27° / 23°C
~21 rain days
Good
October
26° / 22°C
~27 rain days
Good
November
26° / 22°C
~26 rain days
Good
December
25° / 22°C
~20 rain days
Good
Plan around it
Dates locked in? Start from the Koh Samui travel guide or jump straight to a 3-day, 5-day or 7-day itinerary.