UV Index
UV Index
Today's UV index in Ko Samui, Thailand 
will be up to 12.7, indicating a extreme level of sun exposure for the average person. Check our tips for today to make sure you're safe in the sun.
Last checked: 2025-07-18
UV index at 12.7 in Ko Samui means extreme risk: limit outdoor time especially from 10 a.m. to 4 p.m., actively seek shade, wear protective clothing, broad-brimmed hat, apply SPF 30+ sunscreen every 2 hours, and wear UV-blocking sunglasses. Watch for bright surfaces like water and snow increasing UV exposure.
Ko Samui’s UV index is usually very high, often between 8 and 12, meaning the sun’s rays are strong most days, especially around midday.
The island has a tropical climate with three main seasons: a hot season from March to June, a rainy season from October to December, and a cooler, dry season from January to February.
Compared to mainland Thailand, Ko Samui is generally more humid and experiences its rainy season later. It is warmer and less dry than nearby countries like Malaysia and Vietnam during the cool season.
See the UV index hour by hour for Ko Samui, along with the temperature and how cloudy it is. If the UV level is higher than moderate, it's best to avoid direct sunlight.