When To Go · Destination Guide

Koh Samui

Resort comfort on land, Gulf of Thailand pinnacles and marine parks offshore

Updated Jan 23, 2026 • 20 sources

When to go

Best time to visit Koh Samui

Koh Samui sits on the Gulf side of Thailand, so its roughwater season typically peaks later than Phuket and the Andaman coast.

Best overall window

Most reliable islandhopping weather, warm sea, and more consistent tour departures.

Outside that window

Heavier rain and rougher seas. Keep plans flexible and expect occasional cancellations.

Start with the overall answer, then switch only when scuba, freedive, snorkel, or topside timing changes the trip in a meaningful way.

The overall row stays visible so you can compare it against the currently selected scope.

BestGoodTradeoffsMore variable

Scope	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Overall	Overall - Jan: Good	Overall - Feb: Best	Overall - Mar: Best	Overall - Apr: Best	Overall - May: Best	Overall - Jun: Best	Overall - Jul: Best	Overall - Aug: Best	Overall - Sep: Best	Overall - Oct: Tradeoffs	Overall - Nov: Tradeoffs	Overall - Dec: Tradeoffs

These do not replace the overall planner. Use them only if a specific animal or event is driving your trip dates.

Whale shark chance at offshore pinnacles
Best for Scuba
Mar to May, Sep to Oct
JanFebMarAprMayJunJulAugSepOctNovDec
Sail Rock and Koh Tao pinnacles are the classic "maybe" sites.
Blacktip reef sharks in shallow bays
Best for Snorkel, Scuba, Freedive
Year-round
JanFebMarAprMayJunJulAugSepOctNovDec
Shallow sites like Shark Bay can act as nursery areas.
Sea turtles on reefs
Best for Snorkel, Scuba, Freedive
Year-round
JanFebMarAprMayJunJulAugSepOctNovDec
Green turtles and hawksbill turtles are regular sightings around Koh Tao reefs and can also appear on shallow snorkeling stops in the region.
Songkran water festival
Best for Topside
Apr
JanFebMarAprMayJunJulAugSepOctNovDec
Thailand's New Year celebrations bring playful street water fights and a party atmosphere.
Ang Thong marine park open season
Best for Snorkel, Topside, Scuba
Dec to Oct
JanFebMarAprMayJunJulAugSepOctNovDec
Mu Ko Ang Thong National Marine Park is typically open from midDecember through October.
Koh Tao freediving courses and occasional competitions
Best for Freedive
Year-round
JanFebMarAprMayJunJulAugSepOctNovDec
Koh Tao is one of Thailand's main freediving hubs, with courses running yearround and occasional eventstyle depth camps or competitions.

Mu Ko Ang Thong National Marine Park is typically open from midDecember through October, but exact closure timing can change year to year.

Jan: Good beach weather, but northeast monsoon influence can linger on the water.
Oct to Dec: Heavier rain and rougher seas. Keep plans flexible and expect occasional cancellations.

Built from climate references, access rules, and destination operators. Wildlife timing and route flexibility can shift year to year.