A decision guide: which season to book. Crowds, room rates, boat frequency, events and which resorts and kitchens stay open, season by season. For the raw numbers — rainfall, air and sea temperature month by month — use the Koh Mak weather page instead.
For calm water, clear snorkelling and every boat running, November to February is the best time to visit Koh Mak. If you care more about price and quiet than perfect weather, the green season from June to September is a genuinely good trade — the island is at its greenest and long-stay rates are the lowest of the year. For month-by-month rainfall, air and sea temperature, see Koh Mak weather by month. Seasons feel different on each island, so it is worth reading the Koh Mak vs Koh Kood comparison before you commit to dates.
Peak season on Koh Mak.
Flat calm sea, clear water for snorkelling around Koh Rang, daytime highs around 30–32°C and comfortable evenings. Every resort, restaurant and boat is running, and the ferry timetable is at its fullest. Book accommodation and boats ahead over Christmas, New Year and Thai public holidays.
Warmest water, fewest people.
Temperatures climb into the mid-30s with high humidity. Mornings and late afternoons are the time for cycling, tennis and Muay Thai; middays belong to the pool or a hammock. Sea stays calm and visibility is still good. Rates are lower than peak season and beaches feel private.
Rain in bursts, big discounts.
Rain usually comes as heavy afternoon downpours rather than all-day grey. The island is at its greenest, long-stay prices are at their lowest, and the co-working, gym and training crowd tend to visit now. Fewer boat crossings and occasional weather cancellations — leave a buffer day before an onward flight.
The turn back to dry weather.
Rain eases through the month and resorts that closed for the low season reopen. Prices are still soft and the sea calms down. A good gamble if you want quiet beaches with mostly dry days.