Thailand
Koh Samui in May: weather, sea & travel advice
This month's data profile
Rain shapes the decision
Koh Samui in May is climatically mixed. The average daily high is around 30 °C, and the sea is about 30 °C. With about 26 rainy days it is very wet.
Historical monthly averages, not a weather forecast. Individual days and years can differ substantially.
Rank among 12 monthly averages
50/100 · #12
Warmth
#1
Dryness
#8
Sun
#4
Sea warmth
#1
Published best categories: none
Koh Samui · MayPhoto: Sonia Selivonchik · CC BY-SA 4.0Climate facts
- Average high
- 30 °C
- Average low
- 28 °C
- Sea
- 30 °C
- Rainy days (est.)
- 26 rainy days (est.)
- Sun (est.)
- 7 h/day
- Humidity
- 78 %
Climate evidence with direct month comparison
The highlighted row is the selected month. Precipitation total and rainy days are separate monthly averages.
| Month | Avg high °C | Avg low °C | Rainy days (est.) | Precipitation mm | Sun h/day (est.) | Humidity % | Wind m/s | Sea °C | Score |
|---|---|---|---|---|---|---|---|---|---|
| April | 30 | 28 | 14 | 93 | 7.5 | 77 | 2.9 | 30 | 62 |
| May (selected) | 30 | 28 | 26 | 173 | 6.8 | 78 | 3.3 | 30 | 50 |
| June | 30 | 28 | 25 | 164 | 6.4 | 80 | 4.0 | 30 | 52 |
How do the previous and next months compare?
Baseline: May (50/100)
Positive and negative values show the change from the selected month.
| Score Δ | Average high Δ | Average low Δ | Rainy days Δ | Rain Δ | Sun Δ | Humidity Δ | Wind Δ | Sea Δ | |
|---|---|---|---|---|---|---|---|---|---|
| April | +12 | -0.2 °C | -0.2 °C | -12.7 | -80 mm | +0.7 h | -1.4 % | -0.4 m/s | -0.4 °C |
| June | +2 | -0.5 °C | -0.5 °C | -1.2 | -9.4 mm | -0.4 h | +1.7 % | +0.7 m/s | -0.3 °C |
All twelve months in context
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Where to stay in Koh Samui
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Useful next decisions
Frequently asked questions
How warm is Koh Samui in May?
The average daily high is around 30 °C, with an average daily low of about 28 °C.
Can you swim in Koh Samui in May?
The sea is about 30 °C (very warm).
Does it rain a lot in Koh Samui in May?
The curated estimate is about 26 rainy days per month, not a directly measured long-term average. Total precipitation averages around 173 mm for the month. A rainy day does not mean all-day rain.
When is the best time to visit Koh Samui?
By the climate score, January, February, March and December are the strongest months for Koh Samui. For a beach trip: January, February, March and December. May is not among them.