Koh Samui · Edition 9 September 2026
Best time of year to move to Koh Samui
Arrive in September. It is the emptiest month on Koh Samui, at 38.7% occupancy, and the best month to negotiate a long lease (Samui Property Group, 2026). Do not arrive in November. It is the wettest month of the year at 444.6 mm, against 64.3 mm in February (Ko Samui station normals, 1991–2020). The island still prices November as high season.
Samui is wettest when the rest of the tourist map is dry
The island sits on the Gulf side and catches the northeast monsoon. The Andaman coast is wettest from May to October. Here the rain lands from October to December. Get that backwards and the first year of moving to Koh Samui is mispriced: your flights, your rent, your arrival month.
The pricing calendar is no help, because it was not written for this coast. High season is nominally November to March, and 15 December to 15 January is peak whatever the sky does (horizonhomes-samui.com, 2026). So the wettest month of the year sits inside high season. The occupancy figures contradict that: 76.2% in February, 38.7% in September (Samui Property Group, 2026).
The year, as something to live through
| Month | Rain mm | High °C | What the month is like to live in |
|---|---|---|---|
| January | 126.8 | 29.0 | Drying out. Peak prices to mid-month. |
| February | 64.3 | 29.4 | The driest month and the best. Occupancy peaks at 76.2%. |
| March | 115.8 | 30.4 | Hot and mostly dry. Sunniest month, about 8 hours a day. |
| April | 82.9 | 31.8 | The hottest month, and the worst one for water. |
| May | 131.6 | 32.9 | Phuket's low season starts. Samui's does not. |
| June | 133.6 | 32.7 | Warm and showery. Cheap. Jellyfish season opens. |
| July | 117.0 | 32.3 | European summer refills the island. |
| August | 102.2 | 32.4 | Jellyfish risk peaks. |
| September | 117.5 | 31.9 | Occupancy trough, 38.7%. Least sun, about 4.8 hours a day. |
| October | 294.9 | 30.6 | The monsoon lands. Humidity around 85%. |
| November | 444.6 | 29.7 | The wettest month of the year. |
| December | 263.1 | 29.3 | Wet, then New Year peak pricing regardless. |
Rain and temperature are Ko Samui station normals for 1991 to 2020 (WMO). Sunshine and humidity are weather-and-climate.com, read 10 September 2026. Occupancy is Samui Property Group, 2026.
Box jellyfish belong to that calendar too. Risk runs June to October and peaks July to September. A boy of 13 was killed by a sting just south of Samui on 1 August 2026. Ten cases were confirmed across island hospitals three days later (boxjellyfish.online, September 2026).
October to December is the bad window
Those three months carry 1,002.6 mm between them, just over half the annual 1,994.3 mm. November alone is 444.6 mm. That is not a shower pattern, it is days of rain at a time.
The two rainfall datasets disagree on size and on which month is worst. The WMO normals give 1,994.3 mm a year with November wettest. Weather-and-climate.com gives 1,645 mm a year, October wettest at 296 mm over 20 rain days, and February driest at 44 mm (read 10 September 2026). They differ by about 20% and agree on the shape. CHECK
The steep, often unsealed access roads to the best villas are called challenging in heavy rain by the agencies selling those villas (samuipropertygroup.com, June 2026). Sea crossings get cancelled and some businesses shut. Read how you actually get around the island before you pick an address on a hill.
The air is the one thing you never plan around. There is no significant burning season, and the island scores moderate at 51 US AQI (nomads.com, 9 September 2026). No PM2.5 station series is published for Koh Samui, so there is no local annual figure to set beside the WHO guideline. One crowd-sourced score is all that exists.
April is the trap the rain table hides. It is the hottest month at 31.8 °C, one of the driest at 82.9 mm, and the month the water runs short. Rationing began on 3 August 2026, with production near 16,000 m³ a day against demand near 34,000 m³. The Provincial Waterworks Authority gave no end date, and nothing published as of 10 September 2026 confirms it has ended. CHECK Ask any landlord how many cubic metres the villa's storage tank holds.
The discount you can document is lease length, not season
Agents will tell you October to December is when landlords bend. It is plausible and it is unverifiable, because no portal publishes a Koh Samui rent series by month. CHECK The occupancy trough is the closest real proxy you have.
What is documented is the length of the commitment. A twelve-month lease runs 15 to 20% under a six-month one, and six months is the shortest term that gets a long-stay rate (horizonhomes-samui.com, 2026). Below that you pay holiday monthly: the nightly rate times about twenty-five. That gap dwarfs any seasonal one, and it is the single biggest saving in renting here.
Come in September, and do not sign for a year until January
Land in September. Take a six-month lease, or a shorter let while you look. Live through October, November and December on the road you would have signed for. Then take the twelve-month lease in January or February, once you know what you are buying.
The visa clock argues for the same month. From 15 September 2026, visa-free stays for Western passports fall from 60 days to 30 (Royal Gazette, 31 August 2026). One extension of 30 days costs THB 1,900 ($58). If you plan to stay longer, arrange the Thailand DTV visa before you fly — it can only be applied for from outside Thailand.
A September arrival also leaves 113 days in the calendar year, well under the 180 that make you a Thai tax resident. Take advice before your second year, when a full stay crosses that line.
Not sure the island is the right call at all? Compare all ten cities in this series before you book anything.
What this page does not cover
- The three monthly budgets, all in — THB 28,500, THB 77,600 and THB 207,000 — and the utility line that swings from THB 1,200 to THB 10,000 with air conditioning and a pool pump
- Every route off the island priced side by side: the Bangkok Airways nonstop at THB 2,795–8,000, three ferry operators from THB 80, the sleeper train and the overnight bus
- What trucked water costs per 2,000 litres when the taps rotate, and the tank size to ask a landlord for before you sign
- The visa routes that fit someone moving here, with the money tests and the dates each one changed
All of it is in Koh Samui, honestly — 21 pages, $29. See what's inside