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Thailand

Koh Samui weather in December

Is it warm? Yes. December in Koh Samui is hot: afternoons average 30°C and nights 24°C. Most days (80%) peak between 29°C and 30°C.

Hot · average high

30°C

25°C or more on almost every day.

  • Average low24°overnight
  • Sea28°average, 2022–2025
  • Rainy days10228 mm in the month
  • SkyMostly cloudy71% cloud · 7% clear days

How warm it really gets

Every December afternoon from 2011–2025: 465 days. Most (80%) peaked between 29° and 30°.

Number of December days by daily high, 2011–2025.

December, year by year

The average December high in each year. The warmest, 2023, averaged 30°C; the coolest, 2013, 29°C.

Average December high by year: 2011: 29.3°C, 2012: 30°C, 2013: 29°C, 2014: 29.6°C, 2015: 29.9°C, 2016: 29.3°C, 2017: 29°C, 2018: 29.8°C, 2019: 29.6°C, 2020: 29.4°C, 2021: 29.3°C, 2022: 29.2°C, 2023: 30.2°C, 2024: 29.7°C, 2025: 29.5°C.

Compared with home

Average December highs. Expect rain on about 10 days (228 mm in a typical month).

  • Koh Samui30°
  • Cork10°
  • London10°
  • Dublin9°
  • Belfast9°
  • Manchester9°
  • Glasgow8°

Other months

Koh Samui all year · Where else is hot in December

Warmer in December, not much further

Flying times are estimates from Dublin; Koh Samui is about 13h.

  • Very hot in Dec

    33°C average high

    avg high · 20° at night

    25°C+ on almost every day

    The Gambia

    The Gambia

    Sea
    24°
    Rain
    0 days
    Sky
    Often cloudy
    From Dublin
    ≈ 6h

  • Hot in Dec

    31°C average high

    avg high · 26° at night

    25°C+ on almost every day

    Aruba

    Caribbean

    Sea
    28°
    Rain
    9 days
    Sky
    Some cloud
    From Dublin
    ≈ 9h 15m

  • Hot in Dec

    31°C average high

    avg high · 24° at night

    25°C+ on almost every day

    Jamaica (Montego Bay)

    Caribbean

    Sea
    28°
    Rain
    14 days
    Sky
    Some cloud
    From Dublin
    ≈ 9h 15m

Air: Copernicus ERA5-Land, 2011–2025, matched to the official averages for Koh Samui. Sea: Copernicus ERA5, 2022–2025. Rainy days = days with 1 mm of rain or more, as weather stations count them. Clear day = average cloud cover of 30% or less. These are averages of past weather, not a forecast. Methodology