Weather in Ko Samui in May 2025
Average weather
Average temperature in Ko Samui in May
The temperature in May is +28°C on average, with a range between a maximum of +30°C during the day and a minimum of +25°C at night.
The average maximum temperature goes up 20% by the end of the month, compared with the beginning of the month, from +26°C to +27°C.
Is Ko Samui warm or cold in May?
Ko Samui is typically warm in May.
Maximum temperatures go up compared to the previous month from +27°C to +28°C. The minimum temperature also goes up from +25°C to +25°C.
It’s generally warm, but pack a long-sleeve shirt for evenings.
May is one of the warmest months in Ko Samui, here is the comparison with other months:
Water temperature in Ko Samui in May
Water in Ko Samui in May is Very warm. It varies from +29°C to +31°C, with an average of +30°C. Note that the air temperature is lower than the water temperature, averaging around +28°C.
The water temperature in May is one of the warmest of the entire year:
Can you swim in Ko Samui in May?
Climate in Ko Samui in May
| April | May | June | ||||
|---|---|---|---|---|---|---|
| Avg. temperature | ||||||
| +27°C | +28°C | +28°C | ||||
| Min. temperature | ||||||
| +21°C | +21°C | +21°C | ||||
| Max. temperature | ||||||
| +33°C | +34°C | +33°C | ||||
| Rainfall | ||||||
| 86 mm | 116 mm | 82 mm | ||||
| Wind | ||||||
| 2 m/s | 2 m/s | 3 m/s | ||||
| Avg. water temperature | ||||||
| +30°C | +30°C | +30°C | ||||
| Humidity | ||||||
| 78% | 78% | 77% | ||||
| Air pressure | ||||||
| 1008 HPa | 1008 HPa | 1007 HPa | ||||
| Sunny days | ||||||
| 3 | 0 | 0 | ||||
| Cloudy days | ||||||
| 6 | 2 | 4 | ||||
| Rainy days | ||||||
| 12 | 12 | 15 | ||||
| Snowy days | ||||||
| 0 | 0 | 0 | ||||
May weather is still as ok as in April. It’s getting warmer as May arrives. The average maximum temperature goes up from +27°C to +28°C during the day. Prepare for more rain. Average rainfall goes from 86 mm to 116 mm. Humidity levels don’t change as the month goes on, averaging around 78%. The average wind speed doesn’t change much during May, staying around 2 m/s. The days becoming less sunny, going from 3 sunny days in April to 0 in May.
June brings much the same weather, it remains ok.
Wind
The average wind speed is 3 m/s getting up to 4 m/s which is a light breeze; barely moving the tree leaves.
The average wind speed in Ko Samui is gradually increasing during May, going from 3 m/s to 4 m/s over the course of the month.
Rain
How was the weather last May in Ko Samui?
Climate Change over Years
The climate in Ko Samui in May has not changed much over the last 43 years.
The average temperature was the lowest in 1986 (+26°C) and the highest in 2012 (+28°C). The driest year was 1997 with only 927 mm of rainfall, and the wettest year was 1999 with 1981 mm.
FAQ
Is May a good time to visit Ko Samui?
Can you sunbathe in Ko Samui in May?
Can you swim in Ko Samui in May?
Is Ko Samui rainy in May?
Is it sunny in Ko Samui in May?
Other cities in Thailand
Monthly weather in Ko Samui
Source of the data
For this page, we’ve looked at the typical weather in Ko Samui, based on historical hourly weather data from January 1, 1979, to December 31, 2023.
For past dates, we show actual recorded data at the location at that time. Forecasts are based on recorded weather during that day of the year, averaged over the total years for which we have records (unless stated otherwise). The daily temperature is the highest recorded temperature in the shadow during that day.