Overview
Thailand's Andaman coast has two distinct seasons driven by the monsoons. The dry northeast monsoon (November–April) is the only practical window for sailing, bringing settled weather, light winds, and calm seas. The southwest monsoon (May–October) brings heavy rain, strong winds, and rough water that closes most charter operations.
Peak season: December–February
The peak runs December through February — bone-dry, sunny, and warm, with gentle 10–15 knot breezes and flat seas. This is the most reliable weather of the year. It's also the busiest and priciest, so book several months ahead.
Shoulder months: November & April
November marks the end of the wet season — greener landscapes, fewer crowds, and good value, with the occasional late shower. April is hot and humid as the dry season ends, but still sailable, with the best prices before the monsoon closes the season.
What to avoid
Avoid May through October. The southwest monsoon brings sustained strong winds, heavy rain, and big swells on the Andaman coast. Most charter companies don't operate, and conditions are unsuitable for relaxed cruising.
Month-by-month breakdown
Here's how the Andaman year actually unfolds, month by month:
| Month | Weather | Wind & sea | Verdict |
|---|---|---|---|
| Jan | Dry, sunny, 24–32°C | NE 10–15kt, calm seas | Excellent — peak |
| Feb | Driest month of the year | NE 10–15kt, flat water | Excellent — peak |
| Mar | Hot, humidity building | Lightening NE breeze | Very good |
| Apr | Hottest month, hazy | Light, variable | Good — shoulder, Songkran |
| May | First monsoon rains | SW winds building | Avoid — season closing |
| Jun | Wet, frequent squalls | SW 15–25kt, swell | Avoid |
| Jul | Wet season | SW winds, rough west coast | Avoid |
| Aug | Heaviest rain months begin | SW winds, big swell | Avoid |
| Sep | Wettest month | SW winds, rough | Avoid |
| Oct | Rain easing late month | SW dying down | Avoid — transition |
| Nov | Season opens, green landscapes | NE filling in, settling seas | Good — quiet, good value |
| Dec | Dry season established | NE 10–15kt | Excellent — books out at holidays |
Festivals and events worth planning around
Two dates matter for charterers. The King's Cup Regatta, Asia's biggest sailing regatta, runs out of Phuket in early December — a spectacular week if you want atmosphere, a busy one if you want quiet anchorages. Songkran, the Thai New Year water festival (April 13–15), turns every town into a nationwide water fight — chaotic, joyous, and worth experiencing ashore, though provisioning runs and transfers get slow. Loy Krathong, on the November full moon, fills the water with candle-lit floats and is magical seen from an anchorage.
Around Christmas and New Year, charter prices peak and boats book out months ahead; the same weather in mid-January typically costs 15–25% less.