Koh Phangan in the Rainy Season: October to December Guide

The Gulf runs on a different calendar

The single most useful thing to know about Koh Phangan's weather is that it does not match the Thailand most people picture. Phuket and Krabi face the Andaman Sea and get their heavy rain from May to October. Koh Phangan sits in the Gulf, on the other side of the peninsula, and its wet months land late in the year. On the Gulf islands the rainy season runs roughly October to December, with November typically the wettest month .

The numbers are blunt. Long-term averages for nearby Koh Samui, which shares this weather almost exactly, run 275 mm in October, 463 mm in November and 188 mm in December, against 39 mm in February . So November carries more than ten times February's rain. One analysis puts the chance of significant rain on any given November day at about 53%, with October close behind at 49% .

That is not the same as a washout. A wet-season day here is usually long bright mornings and a heavy, theatrical afternoon, with October showers tending to arrive in the late afternoon and evening . The pattern that catches people out is the other kind: three or four days of grey, unbroken rain with wind behind it, which does happen, most often in the second half of November.

As I write, on 8 October 2026, the Thai Meteorological Department has the south-west monsoon still over the country with a high-pressure system pushing down from China, and warnings of isolated heavy to very heavy rain across the South on several days between 9 and 13 October . That is the season announcing itself roughly on time.

What actually gets cancelled

Rain alone changes very little on land. Wind and swell change the boats.

Ferries. Crossings stop when the sea is bad, and the small, fast, direct services go first. When Lomprayah suspended Gulf sailings over three days in January 2025, it was the direct speedboat routes that were cancelled . The larger vehicle ferries between Thong Sala and Donsak are the most stubborn, so if the forecast is ugly and you have a flight, the slow boat and a van is usually the safer booking than the quick catamaran.

Check who actually refunds you before you book. Lomprayah tickets sold through agents are generally non-refundable , and operators reserve the right to cancel, postpone or substitute transport in bad weather or on government orders . In practice you will usually be moved to the next available sailing rather than paid out.

Boat trips. Ang Thong Marine Park is normally closed from 1 November to around 15 December, depending on conditions , and day trips to Koh Tao and Sail Rock thin out in the same window. Diving carries on between fronts, but a booked snorkelling day in late November is a coin toss.

Flights. Samui airport keeps running through ordinary rain. The risk is not the plane, it is getting to the plane.

The practical rule: in October and November, leave a buffer night before any international flight. Cancellations here tend to last a day or two, not a week, and a night on Samui costs far less than a missed connection.

Floods, runoff and the roads

Koh Phangan is a granite dome with a thin skirt of flat land. When a lot of rain falls quickly, it does not soak in; it runs off the hills and crosses the lowest ground on its way to the sea. The water comes fast and leaves fast. After one heavy downpour, runoff from the hills behind Thong Nai Pan carried a parked pickup down to the mouth of a canal .

The big one in recent memory was late November 2025, when severe flooding hit much of southern Thailand, Surat Thani province included . By early December the Tourism Authority of Thailand reported infrastructure operating, transport resumed and tourist activities open across the region, with Koh Samui, Koh Phangan and Koh Tao listed as fully accessible . Worth holding both halves of that: it was genuinely bad, and the islands were functioning again within a fortnight.

Day to day, the thing that will actually affect you is the road surface. Phangan's concrete hill sections are steep, and wet concrete with a film of mud on it is the reason most low-season scooter injuries happen. If it is raining hard, wait twenty minutes. If you are going anywhere hilly, take a car. Jungle tracks that are fine in March turn into running water, and the steeper trails are not worth attempting in a downpour.

The upside is real: this is when the island is at its greenest and when the waterfalls genuinely run, which is covered in more detail in our guide to when they actually flow.

Should you come in November?

Come if you want the island nearly to yourself, at the lowest rates of the year, and your plans are mostly land-based: yoga, food, reading, massage, slow days. Up on the ridge at Ullassa the rain is something you watch arrive across the water from Samui, usually for an hour, with the valley steaming afterwards.

Do not come in November if the trip is built around boats, snorkelling or a tan, or if you have no slack in your schedule at either end. Those holidays belong to late January through March, when the Gulf is at its driest and calmest.

A few things that help:

• Watch the TMD seven-day forecast rather than a phone weather app; the apps show rain icons for the whole fortnight and tell you nothing.
• Book accommodation that is comfortable to be inside for a day. In the wet months this matters more than the beach it sits near.
• Keep one flexible day at each end of the trip.
• Expect mosquitoes to be worse for a few days after heavy rain, and cover up at dusk.
• Dry-bag anything electronic you carry on a scooter.

December turns quickly. Rain here often runs into the first weeks of December and then stops , and the island refills for Christmas. Mid-December onwards is the best-value fortnight of the whole high season if you can read a forecast and take the chance.