Short answer
May is when the Phuket monsoon begins: the Thai Meteorological Department's 1981–2010 normals give 259.5 mm of rain over 18.8 rainy days, up from 142.9 mm in April. The sea is calm early in the month and rougher on the west coast later, the Similan Islands close after 15 May, and hotels are 30–50% cheaper according to Phuket 101. Boat days still run, and Phang Nga Bay, which Phuket 101 says is shielded from the swell by its limestone cliffs, is the steadier choice.
May is where the monsoon begins
May is the month the rain comes back for good. The Thai Meteorological Department's 1981–2010 normals for the Phuket station give 259.5 mm over 18.8 rainy days, against 142.9 mm and 11.8 days in April, and a mean daily maximum of 32.8 °C. The department's climate summary says the southwest monsoon usually starts in mid-May, that May is the first month in which the Inter Tropical Convergence Zone, a belt of converging winds and heavy rain, reaches southern Thailand, and that the start date varies from year to year.
The airport station in the north of the island records more: 281.5 mm over 20.2 days. The newer 1991–2020 table printed on Wikipedia's Phuket City page gives 236.9 mm and 15.7 days with 1 mm or more, with a mean maximum of 33.2 °C. Humidity is 79 percent and sunshine falls to 151.9 hours, about 4.9 hours a day, in the Royal Irrigation Department's figures on Wikipedia's Phuket Province page. Expect heat and humidity with rain on most days, not all day.
The sea in May: calm at first, rougher later
The sea changes during the month. Phuket 101 says it is usually still calm in early May, then the monsoon brings the first swells and potentially dangerous currents to west-coast beaches, with red flags appearing more often. It rates the month as moderate, with waves on the west coast, and gives the water temperature as 30 °C. The Thai Meteorological Department's climate summary says winds turn to the south, southwest and west during the southwest monsoon, and Phuket 101 says the west-coast beaches get their worst waves from May to October.
Phuket 101's monsoon tips add that east-coast beaches such as Ao Po and Cape Panwa stay calmer. Wikivoyage notes that Phuket's marinas are all on the east side, the natural starting point for Phang Nga Bay. For swimming from a beach in the second half of May, read the flags, and see our guide to rip currents and red flags in Phuket. For a boat day, where the boat goes matters as much as the date.
Why Phang Nga Bay is the steadier boat day in May
Phang Nga Bay is protected from the open sea. Phuket 101 says the limestone cliffs shield it from the monsoon swells, and in its August guide that the sea there is always calm, so motion-sickness medicine is not needed. We would treat "always" with care, because the crossing and the weather still vary. Our James Bond Island and Phang Nga Bay canoe tour leaves from Laem Nga pier on Koh Siray at about 9:00 am.
The day is from $85 per person for about 8.5 hours, with hotel pickup between about 7:00 and 8:00 am and a return to the pier at about 5:00 pm. The price includes the national park fee, lunch at Koh Panyee, snorkelling gear, drinks and fruit on board, and sea canoeing at Hong Island with a professional paddler, so you do not need canoeing experience. If the sea is unsafe, the operator moves the trip to another date or refunds it. The details we hold list no closed season for this day, and we confirm your date on WhatsApp before you pay.
What closes in mid-May, and what stays open
The Similan Islands and the Surin Islands close in mid-May, usually around 15 May, and reopen in mid-October, according to Phuket 101. Our Similan Islands speedboat day runs from 15 October to 14 May. Phuket 101 advises booking in the first two weeks of May, and says operators sometimes cancel trips in the second week if conditions look rough. Our Similan season guide gives the dates and the daily quota.
Phi Phi and Phang Nga Bay stay open all year, says Phuket 101, though the seas can be rougher. Maya Bay on Phi Phi Leh is open in May and closes on 1 August, so May is still a month in which you can land there. Our Phi Phi and Maya Bay speedboat tour is from $75 per person; the open-sea crossing can be bumpy, and we compare the two days in our Phi Phi or James Bond Island guide.
Prices and crowds: the low season begins
May marks the start of the low season, and hotel prices fall. Phuket 101 says rooms can cost 30–50% less than in high season, beaches are less crowded, restaurants are easier to book, and many hotels add extras such as free breakfast or spa credits. It calls May one of the best months for budget travellers who do not mind occasional rain.
Tour prices move less than hotel prices. In its June guide, Phuket 101 says the price of food, tours and shopping never really changes in low season, while bargaining in markets gets easier. Our own quote for the Phang Nga Bay day stays "from $85 per person" and we confirm the total for your date and group before you pay. The saving in May is mostly in the room, not on the boat.
May on land: humid days, first rains and mango season
May is humid and the vegetation is dry at first. Phuket 101 says the island looks brown after months without rain, that some waterfalls run dry until the rains pick up, and that the first showers bring relief from the heat, and mosquitoes. It adds that April to June is when mangoes are at their sweetest, so mango sticky rice is the dessert to look for. Surfers also start arriving on west-coast beaches such as Kata, Kalim and Surin as the swells build.
Two public holidays fall in or near May. Wikipedia's list of Thai public holidays gives Coronation Day on 4 May, and Visakha Bucha on the full moon of the sixth lunar month, in May. Phuket 101 says temples hold candlelit processions on Visakha Bucha and that it is a quieter, more reflective time on the island. The dates of lunar holidays move each year, so check the calendar for your trip.
What to pack, and who May suits
Pack light, breathable clothes, a compact umbrella or light rain jacket, waterproof sandals and a waterproof bag for your phone and camera, as Phuket 101 advises, plus insect repellent. For the Phang Nga Bay day, bring swimwear, a towel (towels are not included), sunscreen, a hat and a dry bag for your phone in the canoe. Low tide can change the order of the stops or shorten the canoe route into the lagoon, and the guide times James Bond Island around the tide and the crowds.
May suits visitors on a budget, anyone who likes quiet beaches, and those who can accept some rain. It suits the Phang Nga Bay day better than the open-sea days. It does not suit anyone who needs a guaranteed swim at a west-coast beach, or who has set their heart on the Similans after 15 May. The speedboat is not suitable for pregnant women, infants under 1 year or guests over 70. For the weeks ahead, read Phuket in June; for the months before, Phuket in April.
Practical checklist
- Book the Similan Islands in the first two weeks of May, or choose another month.
- Keep a spare day in your plans in case the operator moves a boat trip because of the sea.
- Pack a light rain jacket, waterproof sandals, insect repellent and a dry bag.
- Read the beach flags before swimming at any west-coast beach, and treat red flags seriously.
- Ask us to confirm your Phang Nga Bay date on WhatsApp before you pay.
Questions and answers
Is May in Phuket the start of the rainy season?
Yes. The Thai Meteorological Department's climate summary says the southwest monsoon usually starts in mid-May. Its 1981–2010 normals for Phuket give 259.5 mm over 18.8 rainy days in May, against 142.9 mm and 11.8 days in April.
Are the Similan Islands open in May?
Until about 15 May. Phuket 101 says the Similan and Surin Islands close around then and reopen in mid-October, and our Similan tour runs from 15 October to 14 May. Book in the first two weeks.
Does the James Bond Island tour run in May?
Yes. The details we hold for the day list no closed season, Phuket 101 says Phang Nga Bay stays open all year, and its limestone cliffs shield the bay from the swell. If the sea is unsafe, the operator moves the trip or refunds it.
Is the sea rough in Phuket in May?
It can be. Phuket 101 says it is usually calm in early May, with swells, red flags and dangerous currents on west-coast beaches more common later. East-coast beaches stay calmer.
How much cheaper is Phuket in May?
Phuket 101 says hotel rooms can be 30–50% cheaper than in high season. Tour prices change less, so the saving is mostly in the room.