Phuket Water Temperature by Month: Is the Sea Warm Enough?

Featured image: Vyacheslav Argenberg, CC BY 4.0, via Wikimedia Commons.

Phuket water temperature: the quick answer

The Andaman Sea around Phuket is a warm part of the Indian Ocean. One seasonal guide puts it above 25°C (77°F) all year. For January and February it gives 28–30°C (82–86°F). Daily records for April show a 28°C minimum, a 30°C average and a 32°C maximum. Model-based monthly averages are tighter still. They list May as warmest at 90.8°F and September as coolest at 89.1°F, a gap under 2°F. Sources differ by a few degrees because they mix satellite, model and buoy methods. None of them describes water cold enough to need heating. The variable that changes your trip is sea state. For the dive-specific view, see our guide to the Best Time to Dive Phuket: Month-by-Month Guide.

Phuket sea temperature by month

No single public dataset gives a clean month-by-month table for Phuket, so this table shows what each period feels like rather than inventing a row of degrees. Temperatures stay in the 28–32°C band quoted above. Sea state is what moves. Treat the sea-state column as typical tendencies, not a forecast.

Warm water vs good conditions: monsoon season explained

Warm does not mean calm. April is hot and the sea is usually flat. From the second half of May, the southwest monsoon brings rain, swell and stronger currents to the Andaman coast. Beaches such as Kata, Karon and Patong face open water, so they feel this first. Afternoon or overnight storms are typical, and skies often clear afterward. In September, beaches commonly carry warnings for high winds and rough seas. Red flags mean stay out of the water, however warm it feels. Visibility underwater also drops when swell stirs up sediment. For a fuller verdict on conditions, read whether Phuket is good for diving. Season also changes what you see, as covered in the guide to Phuket Marine Life: What You'll See, Where and When.

Does temperature differ by beach or dive site?

Surface temperature barely differs between west-coast beaches. Daily records list Kamala, Patong, Karon, Nai Harn and Nai Yang side by side because their readings are so close. Calm is what differs. Phang Nga Bay stays relatively sheltered even when the open coast turns rough, so it is the usual fallback in monsoon weeks. Offshore sites such as the Similan Islands, Racha Islands and Phi Phi sit in deeper water. Divers sometimes meet cooler layers at depth, called thermoclines. No public source gives reliable Phuket numbers for them, so ask your operator what the water felt like on the previous day's dives. The Phuket diving overview covers the main sites.

What to wear: swimming, snorkeling and diving

At 28°C or above, swimmers need nothing but sun protection. Snorkelers often add a rash guard for the sun rather than for warmth. Divers have more to weigh. Dive length, repeated dives in a day and your own cold tolerance all matter. Long sessions can chill even in warm water. PADI describes Thailand as a year-round dive destination in its Thailand dive travel overview. Specific wetsuit thickness depends on your operator's advice.

Best month for your plan

Pick the month by activity, not by degrees. Calm months suit most plans. Low season brings discounts and cancelled boat trips, so keep your itinerary flexible. Beginners should aim for calm water, which makes a first breath underwater easier. Our discover scuba diving guide explains the first-day format. If you want certification, the Phuket Dive Course: PADI Options, Costs & How to Choose page covers timing. To compare costs between seasons, see Phuket diving prices.

Checking conditions before you go

Look at the Thai Meteorological Department's marine forecast and warnings the evening before a boat day. On the beach, red flags override everything. Ask your operator directly about swell, visibility and the plan if the trip is cancelled. Boat departures can be cancelled in rough weather, so a Phuket Diving Day Trip: Sites, Times, Costs works best with a spare day. If you stay on the island, a dive resort can usually re-plan the day for you. Divers should also read the Divers Alert Network guidance on hydration and safe diving.

Common mistakes to avoid

These four errors cause most weather-related disappointment.

• Assuming warm water means calm water.
• Booking an offshore trip in rough-water months.
• Ignoring sun and dehydration on boat days.
• Skipping thermal protection on a multi-dive day.