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.
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.