Phuket dive season runs November to April. Peak window: February to March for whale sharks at Richelieu Rock, manta rays at Koh Bon, and 25-30m visibility on the Similan and Surin liveaboard routes. Avoid June through September entirely — Similan National Park closes and most reputable operators shut their boats. Day trips to Phi Phi run year-round on the calmer side of the island.
The numbers that matter
Water temperature range
Visibility range by month
Liveaboard season
Whale shark window
The Andaman Sea is fully exposed to the southwest monsoon. From May to October, swells, surface chop, and runoff from the mainland combine to drop visibility, close national parks, and ground most boats. The Gulf of Thailand on the other side of the country (Koh Tao, Koh Samui) runs on an opposite calendar — useful to know if your dates fall in the wrong half of the year for Phuket.
Month-by-month breakdown
| Month | Conditions | Visibility | What to expect |
|---|---|---|---|
| Nov | Recovery from monsoon | 15-20m | Liveaboards starting mid-month; day trips return |
| Dec | Peak season opens | 18-25m | High tourist density; prices climb hard from the 20th |
| Jan | Calm, busy, expensive | 20-30m | The reliable month — flat seas, full operations |
| Feb | Whale shark season builds | 20-30m | Richelieu Rock and Surin hitting their stride |
| Mar | Best visibility, manta peak | 20-30m | The single strongest month if you can handle crowds |
| Apr | Hot, end of season | 18-25m | Songkran mid-month; crowds thin in the second half |
| May | Pre-monsoon | 12-18m | Some operators close; reduced liveaboard schedules |
| Jun-Sep | Monsoon — avoid | 8-15m | Similan and Surin closed; most shops shut |
| Oct | Late monsoon | 10-15m | Most operators still closed; conditions improving slowly |
What each season actually feels like
November: the slow opening
Phuket does not flip a switch in November. The first half of the month is often still rough, with afternoon storms and visibility lingering around 12-15m. By mid-month, the southwest monsoon has fully retreated and the first liveaboards start running to the Similan Islands.
If you arrive in early November, you can dive — day trips to Phi Phi and the local sites around Phuket work fine — but you are gambling on whether the offshore parks are open yet. Khao Lak boats typically advertise their first Similan trips around November 15-20. Book later in the month if Similan or Surin is the whole reason for your trip.
December: the season fills up
By December the Andaman is in full season mode. Visibility climbs to 18-25m, surface conditions are calm, and every liveaboard from Khao Lak is running. The price changes too — accommodation, dive packages, and liveaboard cabins jump 20-40% from December 20 through January 5 for the Christmas and New Year window.
Day trips to Phi Phi, Racha Yai, and Racha Noi are reliable. Local Phuket dive sites such as Shark Point and Anemone Reef can hit 20-25m visibility on a good day. The downside is sheer tourist density — Phi Phi sees thousands of snorkellers daily by Christmas week.
January: the calm peak
January is the most stable month of the year. Seas are flat, visibility is consistent at 20-25m on most sites and up to 30m at the better offshore reefs, and water temperature sits at a comfortable 28°C.
The trade-off is price and crowds. January prices are still high, especially the first week, and dive sites can be busy. If you want the calmest seas and most predictable conditions but do not need whale sharks or manta rays specifically, January is the safe choice.
February to March: the whale shark window
This is the peak peak.
The Similan and Surin Islands, plus Richelieu Rock further north, all hit their best conditions in February and March. Whale shark sightings concentrate at Richelieu Rock and around the Surin reefs in this window — the empirical pattern from Khao Lak liveaboard operators is consistent across most years.
Manta rays appear at Koh Bon and Koh Tachai (when accessible) through February and March, with sightings most frequent in late February to mid-March. Visibility runs 25-30m at the offshore sites and around 20m for day trips.
If you can only come to Phuket for one window, make it the last two weeks of February or the first two weeks of March. Book the liveaboard six months ahead — the good operators sell out for this window.
April: hot, fading, still good
April brings the hottest weather of the year. Land temperatures hit 35°C and humidity climbs. Underwater, conditions are still excellent — 20-25m visibility, calm seas, water at 29-30°C — but afternoon storms become possible by late April.
Songkran festival runs April 13-15. The whole country becomes a water fight. Phuket is more chaotic than Koh Tao during Songkran because of the higher tourist concentration. Some divers love it, others find it disruptive. Plan transit days around it if you can.
By the last week of April, some liveaboards begin tapering their schedules. The full Similan-Surin-Richelieu loops start to thin out. Day trips continue normally.
May: pre-monsoon, reduced operations
May is the inflection month. Liveaboard operators close their offshore programs in the first half of May. Similan National Park officially shuts to overnight visitors mid-May. Most reputable Khao Lak operators end their season around May 10-15.
Day trips out of Phuket town to Phi Phi, Racha Yai, and the local sites continue, but the offshore reefs are off-limits. Visibility drops to 12-18m as runoff from the mainland increases.
If your trip is forced into early May, focus on Phi Phi day trips, accept that you are not going to Similan, and check operator schedules carefully — some shops are already winding down.
June to September: the closed season
Similan and Surin National Parks are closed. Most Khao Lak liveaboards are shut. Visibility on local sites drops to 8-15m. Surface conditions range from choppy to outright unsafe.
Phi Phi day trips technically run year-round but conditions are degraded. If your dates fall here, fly to Koh Tao or Bali instead — Phuket is not the destination you booked.
October: late monsoon, still slow
October is the tail. Storms thin in the second half but most operators stay closed. The first Khao Lak liveaboards return mid-November. Do not plan on Similan in October — it is closed until November 15 at the earliest.
The liveaboard question
Phuket dive trips split between day trips out of Phuket town and liveaboards out of Khao Lak.
| Liveaboard route | Season | Highlights |
|---|---|---|
| Similan Islands (3-4 nights) | Mid-Nov to mid-May | Granite boulders, pelagics, Elephant Head Rock |
| Similan + Surin + Richelieu Rock (5-6 nights) | Dec-April | Whale sharks, manta rays at Koh Bon |
| Mergui Archipelago (Myanmar) | Nov-April | Remote, requires Myanmar permits |
Khao Lak departures run November 15 through May 10. Peak February and March routes book out 4-6 months ahead — if you are not booked by October, you are looking at second-tier operators.
Day trips run year-round. December-April reach Phi Phi, Racha Yai, Racha Noi, Shark Point, and Anemone Reef. May-November are restricted to closer sheltered sites.
Prices and crowds
- Cheapest: May to October — but limited site access and weather risk
- Mid-price: Early November, late April, early December
- Most expensive: December 20 to January 5, Chinese New Year, the whale shark peak late February to mid-March
Liveaboard prices swing 25-40% between off-peak and peak. A 4-night Similan trip is around 35,000 THB in early December and 55,000 THB in March.
Peak crowds hit December 20 to January 10, Chinese New Year, the whale shark peak in March, and Songkran (April 13-15). Quieter weeks: early November, early May, and the second half of April. The Similan and Surin liveaboards spread divers across many sites so underwater density is manageable even at peak.
Combining Phuket with other Thai dive destinations
If you have two weeks and want both the Andaman and the Gulf of Thailand, March is the magic month: Khao Lak liveaboard for Similan and Surin (5-6 nights), then fly to Bangkok and on to Koh Tao for 4-5 further diving days. February works similarly.
What to pack regardless of month
- 3mm wetsuit. Andaman water sits at 28-30°C but multi-dive days chill you.
- Reef-safe sunscreen. Required at the marine parks.
- Motion sickness tablets. Similan crossings are 3-4 hours and can be rough.
- Dive computer. Deep profiles at Richelieu Rock and Koh Bon make one essential.
- Cash for park fees. Similan and Surin run 500-800 THB per day, separate from the liveaboard fare.
Putting it all together
If you want the best of Phuket, come in the second half of February or first half of March, book a 5-6 night Similan-Surin-Richelieu liveaboard from Khao Lak, and accept that you are paying peak prices for peak conditions.
If those weeks do not work, January is the calm reliable backup, April before Songkran is the quieter shoulder, and November after the 15th is the cheapest legitimate entry into the season.
Do not book Phuket diving for June through September. Choose Koh Tao or Bali instead — both run on the opposite seasonal calendar and offer good conditions in the months when Phuket is closed.
The Phuket dive season is short but very strong. Time it right and the Andaman delivers the best big-animal diving in Southeast Asia. Time it wrong and you are watching the rain from a hotel lobby.