Weather in Thailand in December

December climate overview

Daytime highs across Thailand in December run from 27.0°C (Chiang Mai) to 30.6°C (Bangkok). In Bangkok about 99% of December days reach 25°C. Nights average 22.6°C; the coldest 10% of nights in Chiang Mai fall to 12°C or below.

Rainfall in December

Expect around 10 rainy days (1 mm or more) in December, with Chiang Mai the driest (2 days) and Krabi the wettest (15 days). The wettest December at Bangkok between 1991 and 2020 was 2017 with 48 mm; the driest was 2003 with 0 mm.

Sea temperature

The sea averages 28.2°C around Thailand in December - warmest at Khao Lak (28.7°C). That is comfortable for swimming.

Sunshine and daylight

Around 4.5 hours of sunshine a day on average, out of 11.2 hours of daylight (sunshine estimated from cloud cover).

December against the rest of the year in Thailand

December is the 12th warmest month of the twelve in Thailand. It is 0.3°C cooler than November and 0.6°C warmer in January. The hottest month here is April (32°C) and the coolest December (29°C).

Which part of Thailand in December?

• Most sunshine: Chiang Mai, 7.3 h a day.
• Driest: Chiang Mai, about 2 rainy days.
• Warmest sea: Khao Lak, 29°C.
• Hottest: Bangkok, 31°C by day.
• Coolest (better for walking and cities): Chiang Mai, 27°C.

What to pack for Thailand in December

Based on the averages: summer clothes for the day; a rain jacket - roughly 10 wet days; swimwear - the sea is 28°C.

Similar weather elsewhere in December

Within 1.5°C of Thailand's December daytime average: Zanzibar (30°C, sea 29°C), Kololi (30°C, sea 24°C), Rio de Janeiro (30°C, sea 24°C), Flic en Flac (29°C, sea 27°C), Kerala (29°C, sea 29°C). See the full ranking for December.

Bangkok or Chiang Mai for drier days

Choose Bangkok if you like heat and want a low rain risk: daytime temperatures average 31°C, falling to 22°C at night, with 2 rainy days. Light clothing makes sense, and keeping more demanding outdoor plans away from midday should make the heat easier to manage. Chiang Mai is the cooler option, averaging 27°C by day and 16°C at night, also with 2 rainy days. That makes it a better fit if you want warm afternoons without equally warm evenings. Pack a light layer for after dark rather than assuming the whole country stays hot through the night. Neither destination is guaranteed to stay dry.

Beach weather: warm water, but allow for rain

For a coastal stay, Phuket has the lowest rainy-day average among the beach destinations listed, at 12, compared with 14 in Khao Lak and Koh Samui and 15 in Krabi. It is a relative advantage, not a promise of dry skies. Phuket pairs 28°C days with a 29°C sea, while Khao Lak has both daytime and sea temperatures of 29°C. Krabi is similarly warm, with 29°C days and a 28°C sea. Koh Samui averages 28°C for both, but its 26°C nights offer little cooling after dark. All suit travellers prioritising warm water, provided beach plans can shift when rain arrives. Sea temperature alone does not tell you about swimming conditions.

What to pack and how to plan your days

Treat December as warm-weather travel rather than guaranteed sunshine. The country averages 4.5 hours of sunshine and 10 rainy days, so leave room to adjust outdoor plans rather than relying on clear skies throughout your stay. Breathable clothes, sun protection and a light waterproof are practical choices. Average nights of 23°C suggest little need for heavy layers in warmer destinations, though Chiang Mai is a clear exception. If you are coming from London, where December days average 8°C, Thailand will feel considerably warmer. Give yourself time to adjust to the heat, and use shade and breaks to make long days outside more comfortable.