20-Year Climate Average
Koh Samui, Surat Thani, Thailand Weather in May
Normal High
82°F
Normal Low
76°F
Rainy Days
~27 of the month
Chance of Rain
87%
Humidity
77%
UV index
Not available
Daylight
12.6 hours
Peak wind
11 mph
Usually good for: beaches and outdoor dining.
Based on May climate records from 2006–2025 (Open-Meteo Historical Weather Archive). These are planning averages, not a forecast. Data: Open-Meteo.com, CC BY 4.0.
Current conditions
Forecast versus the climate baseline
81°F
It currently feels like 90°F with 69% humidity, a 70°F dew point and 5 mph wind. Climate averages describe the month; this live reading is what matters for plans today.
82° / 73° · 97% rain
80° / 71° · 100% rain
80° / 72° · 99% rain
Best Months to Visit Koh Samui, Surat Thani, Thailand
Ranked by historical rainy-day frequency — the driest months over the past 20 years.
Methodology
Monthly values use the 2001–2020 observation period. Temperature, precipitation, humidity or dew point, wind, UV and daylight are shown only when the selected source provides them; unavailable fields are never estimated or silently replaced. These are planning normals, not guarantees for a specific trip.
What is the weather like in Koh Samui, Surat Thani, Thailand in May?
The 20-year average high in Koh Samui, Surat Thani, Thailand in May is 82°F, with a low around 76°F and about 27 rainy days.