Koh Samui weather in May 2025

Expect 90°F daytime maximum temperatures in the shade with on average 6 hours of sunshine per day in Koh Samui in May. Check more long-term weather averages for Koh Samui in May before you book your next holiday to Thailand in 2025/2026.

90
90°F max day temperature
6
6 hours of sunshine per day
17
17 days with some rainfall
77
77°F min night temperature
13
13 hours of daylight per day
VH
Very High heat & humidity
6.8
6.8 inches of monthly rainfall
11
11+ (Extreme) UV index
86
86°F sea temperature

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The May weather guide for Thailand (Koh Samui) shows long term weather averages processed from data supplied by CRU (University of East Anglia), the Met Office & the Netherlands Meteorological Institute. Find out more about our data sources.

Metric (°C) | Imperial (°F)

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How hot is it in Koh Samui in May?

Daytime temperatures usually reach 90°F in Koh Samui in May with very high heat and humidity, falling to 77°F at night.

How sunny is it in Koh Samui in May?

There are normally 6 hours of bright sunshine each day in Koh Samui in May - that's 51% of daylight hours.

How warm is the sea around Koh Samui in May?

The average sea temperature around Koh Samui in May is 86°F.

Does it rain in Koh Samui in May?

There are usually 17 days with some rain in Koh Samui in May and the average monthly rainfall is 6.8 inches.

Koh Samui May sunrise & sunset times

Browse the sunrise and sunset times for Koh Samui in May 2025. Select a month to view Koh Samui sunrise and sunset times for the next 12 months.

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Date	Sunrise times	Sunset times
Thursday, 1st May 2025	06:03	18:31
Friday, 16th May 2025	05:59	18:33
Saturday, 31st May 2025	05:58	18:37

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Thailand - quick facts
Flight time^✝	15 hours
Time difference	UK +7 hours
Language(s)	Thai, Isan
Currency	Thai Baht
Electricity	A + B + C + O plug (230V)
Driving side	Left
Why visit?	Beaches Culture Nature Nightlife
Tourist info	Tourism Authority of Thailand