Quick answer: Koh Samui sits at 9.5° N and gets about 12 h 13 min of daylight today, with the sun 85° up at solar noon. The panel above scores each upcoming day 0–100 and returns a direct go, wait or skip verdict.
Conditions on this page are recalculated from the latest forecast every time it is opened, for the current date in the location's own time zone.
One page for Koh Samui, Thailand: today's 0–100 Weather Score with the factors behind it, the hour-by-hour rain outlook, every day of the coming week ranked and colour-coded, and sunrise, sunset and golden hour computed for Koh Samui's own coordinates and timezone. Forecast values load live from Open-Meteo when the page opens; nothing below is a stored or generated climate figure.
Any weather decision in Koh Samui starts from the light budget. In September the location gets about 12 h 13 min of daylight, with the sun peaking 85° above the horizon — that sets how warm afternoons run, how long outdoor plans stay viable and how much usable photographic light the day contains. The scores above layer the live Open-Meteo forecast on top of that baseline.
Daylight, midday sun angle and golden-hour length below are calculated for Koh Samui's own coordinates (9.51° N, 100.01° E) on the 15th of each month. These are solar geometry, not climate averages.
| Month | Daylight | Sun at solar noon | Golden hour |
|---|---|---|---|
| January | 11 h 36 min | 59° | 44 min |
| February | 11 h 48 min | 67° | 42 min |
| March | 12 h 0 min | 78° | 41 min |
| April | 12 h 18 min | 90° | 41 min |
| May | 12 h 36 min | 81° | 43 min |
| June | 12 h 42 min | 76° | 44 min |
| July | 12 h 36 min | 78° | 44 min |
| August | 12 h 24 min | 86° | 42 min |
| September | 12 h 12 min | 83° | 41 min |
| October | 11 h 54 min | 71° | 41 min |
| November | 11 h 42 min | 61° | 43 min |
| December | 11 h 36 min | 57° | 44 min |
Scores are capped by dealbreakers — heavy rain, dangerous wind, thick fog or hazardous UV pull a day down no matter how pleasant the rest of the numbers look. Forecast data is Open-Meteo; solar and lunar values are computed for Koh Samui's own coordinates and time zone. Full details on the methodology page.