Ko Samui, Thailand: vitamin D, best months and travel guide
Gulf island with a mix of luxury resorts and budget bungalows. Best for: couples, families, honeymooners.
The best months for vitamin D in Ko Samui are February, March, June, December, when a full dose takes about 6 minutes at midday. Too hot from April to May and rainy or stormy in January and from July to November.
Ko Samui month by month
| Month | Rating | Sun window | Peak UV | Full dose, age 30 | Afternoon high | Rainy days |
|---|---|---|---|---|---|---|
| January | Bad weather | 7.8 h | 7.7 | 7 min | 29°C | 18/30 |
| February | Excellent | 8.2 h | 8.6 | 6 min | 30°C | 11/30 |
| March | Excellent | 8.5 h | 9.1 | 6 min | 32°C | 7/30 |
| April | Too hot | 8.8 h | 9.2 | 6 min | 34°C | 5/30 |
| May | Too hot | 7.8 h | 8.0 | 7 min | 32°C | 19/30 |
| June | Excellent | 6.9 h | 7.1 | 8 min | 32°C | 16/30 |
| July | Bad weather | 6.7 h | 6.9 | 8 min | 30°C | 24/30 |
| August | Bad weather | 7.9 h | 8.1 | 7 min | 30°C | 26/30 |
| September | Bad weather | 7.1 h | 7.8 | 7 min | 30°C | 21/30 |
| October | Bad weather | 7.1 h | 7.5 | 7 min | 29°C | 25/30 |
| November | Bad weather | 6.5 h | 7.0 | 8 min | 29°C | 23/30 |
| December | Good | 5.9 h | 6.0 | 9 min | 28°C | 16/30 |
Sun window is the number of hours a day with UV Index 2.5 or higher. Full dose is the minutes at midday for about 1,000 IU of vitamin D with a quarter of the body bare, for skin type III. Rainy days are days with at least 1 mm out of 30.
What to expect in Ko Samui
Gulf island with a mix of luxury resorts and budget bungalows. A hot dry season from November to February on both coasts, and monsoon rain from May to October on the Andaman side (Phuket, Krabi). The Gulf side (Samui) is driest in the first months of the year. March to May is very hot.
In Ko Samui afternoon highs average from 28°C in December to 34°C in April. The wettest month is August (about 26 rainy days out of 30) and the driest is April (5). Midday UV peaks at 9.2 in April, which is very strong, so protect your skin.
Comfortable, nature, and entertainment hippie mecca gone upmarket (Wikivoyage, CC BY-SA 4.0)
More about Thailand · Thailand in March · Best places in March
Questions about Ko Samui
When is the best time to visit Ko Samui for vitamin D?
The best months for vitamin D in Ko Samui are February, March, June, December, when a full dose takes about 6 minutes at midday.
What is the weather like in Ko Samui?
Afternoon highs average from 28°C in December to 34°C in April. The wettest month is August, with about 26 rainy days out of 30.
Which months should I avoid in Ko Samui?
For a beach stay, avoid the months when it is too hot from April to May and rainy or stormy in January and from July to November.