- ✓December is the heart of Thailand's cool, dry season: warm sunny days, comfortable nights, and the lowest humidity of the year across most of the country.
- ✓December is often within the Andaman's more settled period, while Phuket, Krabi, Phi Phi and Lanta also see high holiday demand; storms and rough-sea days remain possible.
- ✓On the Gulf side — Samui, Phangan, Tao — the wettest stretch is tailing off through December, so it's improving but still the less reliable coast this month; the Andaman is the safer beach bet.
- ✓This is peak season, and the Christmas-to-New-Year fortnight is the busiest, most expensive window of the whole year — beach hotels and popular routes book out weeks or months ahead.
- ✓Festival dates, New Year programming, prices and ferry timetables all move year to year — settle your region and dates on the evergreen weather pattern, then verify the volatile details before you book.
December weather, region by region
December is the month Thailand's weather is most on your side. For most of the country it's the heart of the cool, dry season — the northeast monsoon has set in, pulling drier air across the mainland, dropping the humidity and clearing the skies. Days are warm and sunny rather than oppressive, nights are genuinely comfortable, and the daily afternoon downpours of the green season are behind you. If you want the single most dependable month to visit Thailand, this is it.
The exception, as always in Thailand, is the Gulf coast. The two seas don't share a season: the Andaman coast in the west dries out for the cool months, while the Gulf islands in the east run on a later, different rainfall pattern and take their heaviest rain late in the year. December sits right at the tail of that Gulf wet stretch — the rain is easing as the month goes on, but Samui, Phangan and Tao can still see showers and the odd unsettled spell while Phuket and Krabi are basking. That contrast is the whole reason December planning hinges on which coast you choose.
Up north, Chiang Mai, Chiang Rai and the mountains are at their crisp, clear best — warm afternoons, properly cool mornings and evenings, and none of the dry-season haze that arrives later in the new year. Bangkok and the central plains enjoy the most pleasant weather of their year too: still warm, but drier and a touch cooler, which makes temple days and street-food evenings far easier than in the hot or rainy months.
Andaman vs Gulf in December — the verdict
For a December beach trip, the Andaman coast wins clearly. This is its peak month: dry days, calm seas, clear water and reliable boat conditions across Phuket, Krabi, Phi Phi, Koh Lanta and Khao Lak. Island-hopping, snorkelling and longtail trips are at their most dependable, and the famous beaches look the way the brochures promise. The catch is that everyone knows this — December is the Andaman's busiest, priciest stretch, and the headline beaches and resorts fill early.
The Gulf islands are the weaker bet this month, but not a write-off. Their heaviest rain falls late in the year and is generally tailing off through December, so conditions improve as the month goes on and the festive period can be perfectly fine — it's simply less of a sure thing than the Andaman, with a higher chance of a showery day or a choppy ferry crossing. If your trip is built around Samui, Phangan or Tao, December can still work; just hold your plans a little loosely and keep an eye on the forecast.
The simple rule for December: if you're choosing a coast from scratch and the weather is what matters most, point yourself at the Andaman. If you're set on the Gulf for other reasons — a Koh Tao dive course, a Samui resort, a wellness retreat on Phangan — go in knowing it's the improving-but-unsettled side this month, and the later in December you travel, the better your odds. Whatever you pick, don't try to do both coasts in one short December trip: crossing the peninsula is a full travel day, not an island-hop.
What to do — and what to skip — in December
December is commonly among the more settled months on the Andaman, but boat and dive days still depend on live marine conditions. The North is typically cooler than in the hot season; air quality is often better than during the later burning period but can still deteriorate, so check PM2.5 before strenuous outdoor plans.
It's a strong culture month everywhere on the mainland: Bangkok's temples, the riverside, the heritage ruins of Ayutthaya and Sukhothai, and the markets are all far more comfortable in December's drier, cooler air than at any other time of year. If you want to pair a city base with a beach, December is the textbook month to do it on the Andaman side.
What to skip, or at least plan around: don't pin a December trip on the Gulf if dependable beach weather is the whole point — the Andaman is the steadier choice. And don't assume you can turn up and find space over Christmas and New Year. The festive fortnight is the one window where popular hotels, internal flights and even some ferries sell out, so spontaneous travel that works fine in the quieter months can leave you stranded now.
Festivals and dates to plan around
December's two fixed dates are civil rather than the lantern-and-water festivals that fall earlier in the year. New Year's Eve, on 31 December, is the big one: countdown celebrations, fireworks and parties run across the country, from Bangkok's riverside and malls to the beach resorts of Phuket, Krabi and Samui. It's a genuine highlight if you want the buzz — and the single reason the surrounding fortnight is so heavily booked and priced. Early December also marks the birthday of the late King Bhumibol Adulyadej (5 December), observed nationally and also as Father's Day, when government offices close and some sites hold commemorations.
Loy Krathong and the Yi Peng lantern festival in Chiang Mai — the floating-light celebrations many travellers associate with Thailand — fall in November, not December, so they're just before this window; if they're on your list, that's a November trip. Check the specific year, because the lunar dates shift.
Because programming, opening times and prices around New Year vary every year and venue by venue, treat any specific date, event or rate here as something to confirm against an official source before you book around it. The weather pattern is the reliable part of December; the festive details are the part to verify.
Crowds, prices and booking ahead
The second half of December is a high-demand period because of school holidays, Christmas and New Year. Popular resorts, internal flights and ferries can sell out and may cost more than earlier December, but it is not possible to rank every destination as the year's single busiest or most expensive period.
The practical takeaway is to flip your usual booking order. In the quiet months you can leave a lot to chance; in December you can't. Lock the things that sell out first — your peak-season beach hotel, any internal flight tied to the festive dates, and long routes like the night train south or a Phuket–Krabi boat day — well ahead, and leave only the small daily choices for when you arrive.
Early December may have lower demand than the Christmas-to-New-Year period, but rates and weather vary. Compare refundable prices and forecasts rather than assuming an early-month bargain.
Best for — who December suits
December suits travellers who want certainty. If you're planning a first Thailand trip and want the most dependable weather, this is the month — sunny, dry, comfortable, and on the Andaman side the beaches are at their best. Couples after postcard limestone bays, families using the school break, and anyone who values a reliable forecast over a quiet beach or a low price will all be well served. It's also the prime month for a culture-plus-coast trip on the Andaman side: Bangkok or Chiang Mai for the cool-weather temples and food, then Krabi, Phuket or a quiet Andaman island to unwind.
It suits you less if your priorities run the other way. If you're chasing value or empty beaches, December's peak prices and crowds work against you — the green season or the early-year shoulder will serve you better. If your heart is set on the Gulf islands specifically, December is workable but not their strongest month; travel later in it and hold plans loosely. And if you can't, or won't, book the festive fortnight well ahead, you'll find the best places gone. Settle your coast and dates on December's reliable weather, then verify the prices, event programming and ferry status before you commit.
Sources and official planning resources
Thailand in December · at a glanceMonth FC
- Season
- Often cooler/drier inland and more settled on the Andaman; the Gulf can remain wet — verify the regional forecast
- Andaman coast
- At its best: dry, calm seas, clear water (Phuket, Krabi, Phi Phi, Lanta, Khao Lak)
- Gulf islands
- Wettest stretch easing off but still the less settled coast — Samui, Phangan, Tao improving through the month
- Crowds & price
- Peak season; Christmas–New Year is the busiest, priciest fortnight of the year
- Festivals
- New Year's Eve (31 Dec) countdowns nationwide; King Bhumibol's birthday / Father's Day (5 Dec)
- Best for
- Beach trips on the Andaman; first-timers wanting the most dependable weather
- Avoid if
- You want low prices or empty beaches, or can't book the festive weeks well ahead
- Book / verify first
- Peak-season beach hotels and long routes early; re-check event dates, prices & ferry status
