Weather in Thailand in January

January climate overview

Daytime highs across Thailand in January run from 27.5°C (Koh Samui) to 31.0°C (Bangkok). In Bangkok about 100% of January days reach 25°C. Nights average 22.6°C; the coldest 10% of nights in Koh Samui fall to 24°C or below.

Rainfall in January

Expect around 7 rainy days (1 mm or more) in January, with Chiang Mai the driest (2 days) and Koh Samui the wettest (10 days). The wettest January at Bangkok between 1991 and 2020 was 2018 with 79 mm; the driest was 2014 with 0 mm.

Sea temperature

The sea averages 27.9°C around Thailand in January - warmest at Khao Lak (28.4°C). That is comfortable for swimming.

Sunshine and daylight

Around 5.6 hours of sunshine a day on average, out of 11.3 hours of daylight (sunshine estimated from cloud cover).

January against the rest of the year in Thailand

January is the 8th warmest month of the twelve in Thailand. It is 0.6°C warmer than December and 1.4°C warmer in February. The hottest month here is April (32°C) and the coolest December (29°C).

Which part of Thailand in January?

• Most sunshine: Chiang Mai, 8.1 h a day.
• Driest: Chiang Mai, about 2 rainy days.
• Warmest sea: Khao Lak, 28°C.
• Hottest: Bangkok, 31°C by day.
• Coolest (better for walking and cities): Koh Samui, 28°C.

What to pack for Thailand in January

Based on the averages: summer clothes for the day; a light waterproof for the odd shower; swimwear - the sea is 28°C.

Similar weather elsewhere in January

Within 1.5°C of Thailand's January daytime average: Rio de Janeiro (31°C, sea 26°C), Zanzibar (30°C, sea 28°C), Guanacaste (30°C, sea 27°C), Kerala (30°C, sea 28°C), Flic en Flac (30°C, sea 28°C). See the full ranking for January.

Bangkok for heat, Chiang Mai for cooler evenings

Bangkok is the hottest option here at 31°C by day, with only 3 rainy days in January. It suits travellers who want mostly dry weather and do not mind planning around midday heat: keep walking for the cooler parts of the day and take shaded breaks. Nights average 22°C, so the warmth eases without turning cold. Chiang Mai offers a different balance, with days at 28°C, nights at 16°C and just 2 rainy days. That makes it a good fit if you prefer warm daytime exploring followed by noticeably cooler evenings. Pack a light layer for after dark rather than assuming the whole country stays warm enough for short sleeves.

Which coast should you choose?

Phuket has a useful balance for a beach stay: days average 29°C, the sea is 28°C and there are 7 rainy days. Krabi is slightly hotter at 30°C, with 8 rainy days and the same sea temperature. Khao Lak also reaches 30°C, but its 10 rainy days mean allowing more flexibility around outdoor plans. Koh Samui matches that rainy-day figure, with days at 28°C and nights at 25°C. It is a cooler daytime choice, not a cooler place to sleep. For less frequent rain among these coastal options, favour Phuket or Krabi. For swimming warmth, there is little to separate them; the bigger differences are rain frequency and how warm evenings feel.