Ko Samui's driest, sunniest stretch, though even in these months a stray shower can pass through. February and March are the driest of all, and by April the heat starts building toward the year's peak. Expect the busiest beaches and highest hotel rates of the year, book Chaweng and Lamai well ahead.

This tier spans very different parts of the year. Early January is still catching the tail end of the rains before the dry season properly begins, while June through September sit in the calmer middle of the monsoon, showers arrive most days but are usually short, and it's common to go a week without rain in July or August. December carries real rain totals too, as the wettest peak from October and November eases but hasn't fully let up yet.

May opens the rainy season with its first real burst of rain alongside the year's hottest temperatures, while October and November bring the true rainy peak, when the retreating monsoon can dump torrential, occasionally flooding rain on the island, November especially. Widely considered the worst time to visit, though hotel prices drop to match.