Very hot in May
36°C average high
avg high · 23° at night
25°C+ on almost every day · often 35°C+
Thailand
Koh Samui weather in May
Is it warm? Yes. May in Koh Samui is very hot: afternoons average 33°C and nights 26°C. Most days (80%) peak between 32°C and 34°C.
Very hot · average high
33°C
25°C or more on almost every day.
- Average low26°overnight
- Sea31°average, 2022–2025
- Rainy days12150 mm in the month
- SkyMostly cloudy82% cloud · 2% clear days
How warm it really gets
Every May afternoon from 2011–2025: 465 days. Most (80%) peaked between 32° and 34°.
May, year by year
The average May high in each year. The warmest, 2023, averaged 34°C; the coolest, 2022, 32°C.
Compared with home
Average May highs. Expect rain on about 12 days (150 mm in a typical month).
- Koh Samui33°
- London19°
- Glasgow17°
- Manchester16°
- Cork16°
- Belfast16°
- Dublin16°
Warmer in May, not much further
Flying times are estimates from Dublin; Koh Samui is about 13h.
Very hot in May
35°C average high
avg high · 25° at night
25°C+ on almost every day · often 35°C+
Very hot in May
34°C average high
avg high · 24° at night
25°C+ on almost every day · often 35°C+
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