January is one of the strongest months in Koh Samui (2nd)
Best window · 9.1/10With 24°C (75°F) on average, January delivers classic beach weather: plenty of time in the water, with beach and boat plans rarely disrupted by cold.
Budget for roughly 56 mm of rain this month — a flexible day or two helps — with about 30 days with 6+ hours of sunshine and 11.6 hours of daylight to work around it.
On our climate-comfort scale this is one of the strongest months of the year for Koh Samui at 9.1/10 (2nd of 12), just behind March at 9.3/10.
Budget for peak pricing, and this is one of the busiest months here. You are paying the year's highest rates for the year's best conditions — book early or shift a few weeks either side.
Pack light clothing, swimwear and real sun protection, a packable rain layer.
February is one of the strongest months in Koh Samui (4th)
Best window · 8.5/10With 24°C (76°F) on average, February delivers classic beach weather: plenty of time in the water, with beach and boat plans rarely disrupted by cold.
Budget for roughly 79 mm of rain this month — a flexible day or two helps — with about 27 days with 6+ hours of sunshine and 11.8 hours of daylight to work around it.
On our climate-comfort scale this is one of the strongest months of the year for Koh Samui at 8.5/10 (4th of 12), just behind March at 9.3/10.
Expect mid-season pricing, and crowds are moderate.
Pack light clothing, swimwear and real sun protection, a packable rain layer.
March: the best month of the year in Koh Samui
Best window · 9.3/10March averages 25°C (77°F) — warm enough for beach and boat plans, still short of the heat that pushes sightseeing into early morning.
Rainfall runs 47 mm, so plan one flexible day in three; you still get about 31 days with 6+ hours of sunshine and 12.1 hours of daylight.
On our climate-comfort scale this is the top-ranked month of the year for Koh Samui at 9.3/10 — the reference point every other month on this page is measured against.
Plan for peak pricing, with this is one of the busiest months here. You are paying the year's highest rates for the year's best conditions — book early or shift a few weeks either side.
Pack light clothing, swimwear and real sun protection, a packable rain layer.
April holds up well in Koh Samui — 5th best month
Good · 8.4/10Days in April average 26°C (79°F) and humidity near 76% — front-load outdoor plans before the heat builds and treat the middle of the day as indoor time.
Budget for roughly 89 mm of rain this month — a flexible day or two helps — with about 28 days with 6+ hours of sunshine and 12.3 hours of daylight to work around it.
That is 8.4/10 on the same scale — 5th of 12 months, versus 9.3/10 for the best month here.
Expect mid-season pricing, and crowds are moderate.
Pack the lightest breathable clothing you own, a hat, and more water than feels necessary, a packable rain layer.
May in Koh Samui — reliably good (8th best month)
Good · 7.6/10May averages 26°C (79°F) and humidity near 79%, so the practical pattern is early mornings, a long midday break, and evenings back outside.
Monthly rainfall reaches 135 mm — wet for this destination — but about 28 days with 6+ hours of sunshine still break through, so keep one indoor fallback in the plan.
It scores 7.6/10 here, 8th of 12 months, against 9.3/10 in the destination's best month.
Figure on low-season pricing, with crowds are light for this destination.
Pack the lightest breathable clothing you own, a hat, and more water than feels necessary, a proper rain shell rather than an umbrella.
Flexible dates? March scores 1.7 points higher here — enough to change the trip.
June is one of the strongest months in Koh Samui (3rd)
Best window · 8.8/10Days in June average 26°C (79°F) and humidity near 75% — front-load outdoor plans before the heat builds and treat the middle of the day as indoor time.
Budget for roughly 72 mm of rain this month — a flexible day or two helps — with about 27 days with 6+ hours of sunshine and 12.7 hours of daylight to work around it.
On our climate-comfort scale this is one of the strongest months of the year for Koh Samui at 8.8/10 (3rd of 12), just behind March at 9.3/10.
Budget for mid-season pricing, and crowds are moderate.
Pack the lightest breathable clothing you own, a hat, and more water than feels necessary, a packable rain layer.
July in Koh Samui — reliably good (6th best month)
Good · 8/10With 26°C (78°F) on average, July delivers classic beach weather: plenty of time in the water, with beach and boat plans rarely disrupted by cold.
114 mm of rain makes this a wet month here, though with about 24 days with 6+ hours of sunshine there is still bright weather between the fronts.
That is 8/10 on the same scale — 6th of 12 months, versus 9.3/10 for the best month here.
Expect mid-season pricing, and crowds are moderate.
Pack light clothing, swimwear and real sun protection, a proper rain shell rather than an umbrella.
August holds up well in Koh Samui — 7th best month
Good · 8/10August averages 26°C (78°F) — warm enough for beach and boat plans, still short of the heat that pushes sightseeing into early morning.
Monthly rainfall reaches 112 mm — wet for this destination — but about 27 days with 6+ hours of sunshine still break through, so keep one indoor fallback in the plan.
It scores 8/10 here, 7th of 12 months, against 9.3/10 in the destination's best month.
Plan for mid-season pricing, with crowds are moderate.
Pack light clothing, swimwear and real sun protection, a proper rain shell rather than an umbrella.
September holds up well in Koh Samui — 9th best month
Good · 7.6/10September averages 25°C (77°F) — warm enough for beach and boat plans, still short of the heat that pushes sightseeing into early morning.
Monthly rainfall reaches 131 mm — wet for this destination — but about 25 days with 6+ hours of sunshine still break through, so keep one indoor fallback in the plan.
It scores 7.6/10 here, 9th of 12 months, against 9.3/10 in the destination's best month.
Plan for low-season pricing, with crowds are light for this destination.
Pack light clothing, swimwear and real sun protection, a proper rain shell rather than an umbrella.
Flexible dates? March scores 1.7 points higher here — enough to change the trip.
October in Koh Samui — middling scores, decent value
Trade-offs · 6.7/10With 24°C (76°F) on average, October delivers classic beach weather: plenty of time in the water, with beach and boat plans rarely disrupted by cold.
This is the year's wettest stretch at 235 mm, but with about 25 days with 6+ hours of sunshine it is not a total loss; an indoor fallback covers the risk.
That is 6.7/10 on the same scale — 11th of 12 months, versus 9.3/10 for the best month here.
Expect low-season pricing, and crowds are light for this destination.
Pack light clothing, swimwear and real sun protection, a proper rain shell rather than an umbrella.
If your dates are flexible, March is materially better in Koh Samui — 2.6 points higher on the same scale.
November in Koh Samui — middling scores, decent value
Trade-offs · 6.5/10With 24°C (75°F) on average, November delivers classic beach weather: plenty of time in the water, with beach and boat plans rarely disrupted by cold.
This is the year's wettest stretch at 346 mm, but with about 22 days with 6+ hours of sunshine it is not a total loss; an indoor fallback covers the risk.
That is 6.5/10 on the same scale — 12th of 12 months, versus 9.3/10 for the best month here.
Expect low-season pricing, and crowds are light for this destination.
Pack light clothing, swimwear and real sun protection, a proper rain shell rather than an umbrella.
If your dates are flexible, March is materially better in Koh Samui — 2.8 points higher on the same scale.
December in Koh Samui: strong conditions, 10th of 12
Good · 7.1/10December averages 24°C (75°F) — warm enough for beach and boat plans, still short of the heat that pushes sightseeing into early morning.
Monthly rainfall reaches 171 mm — wet for this destination — but about 27 days with 6+ hours of sunshine still break through, so keep one indoor fallback in the plan.
It scores 7.1/10 here, 10th of 12 months, against 9.3/10 in the destination's best month.
Figure on mid-season pricing, with crowds are light for this destination.
Pack light clothing, swimwear and real sun protection, a proper rain shell rather than an umbrella.
Flexible dates? March scores 2.2 points higher here — enough to change the trip.
