Thailand's two coasts have opposite seasons, and that should shape where you buy. The Andaman coast is dry from December to March and wet from May to October. Koh Samui, on the southern Gulf, takes its heavy rain from October to December and is dry from February to April. The upper Gulf towns of Hua Hin and Pattaya are drier than either all year. The north is cool in winter and smoky in spring.
The three seasons and two monsoons
Thailand's year has three seasons:
- Hot season, mid-February to mid-May.
- Rainy season, mid-May to mid-October, driven by the south-west monsoon from the Indian Ocean. August and September are the wettest months for most of the country.
- Cool season, mid-October to mid-February, driven by the north-east monsoon, which brings cooler, dry air to most of Thailand.
The southern peninsula, where most resort property is, behaves differently. The south-west monsoon hits the west-facing Andaman coast directly. The north-east monsoon brings heavy rain to the east-facing Gulf coast around Koh Samui, peaking from November to January.
Rainfall month by month
Average monthly rainfall in millimetres.
| Month | Phuket | Krabi | Koh Samui | Hua Hin | Pattaya | Chiang Mai |
|---|---|---|---|---|---|---|
| January | 30 | 32 | 127 | 25 | 16 | 11 |
| February | 24 | 43 | 64 | 14 | 20 | 10 |
| March | 74 | 98 | 116 | 51 | 47 | 20 |
| April | 143 | 147 | 83 | 47 | 68 | 54 |
| May | 260 | 172 | 132 | 96 | 121 | 168 |
| June | 213 | 193 | 134 | 82 | 132 | 118 |
| July | 258 | 201 | 117 | 90 | 104 | 149 |
| August | 287 | 266 | 102 | 67 | 91 | 223 |
| September | 361 | 275 | 118 | 130 | 214 | 207 |
| October | 320 | 324 | 295 | 250 | 225 | 124 |
| November | 177 | 180 | 445 | 73 | 57 | 41 |
| December | 72 | 68 | 263 | 12 | 12 | 14 |
| Year | 2,220 | 1,999 | 1,994 | 936 | 1,106 | 1,139 |
Phuket figures are for Phuket Town. The airport station, in the north of the island, is wetter at about 2,475 mm a year.
The Andaman coast: Phuket and Krabi
The dry season runs from December to March. This is when Phuket and Krabi earn most of their rental income, and when owners from Europe want to be in residence.
From May the south-west monsoon arrives. Phuket Town averages 18 to 23 rainy days a month from May to October, and September and October each bring more than 300 mm. The practical issue is the sea as much as the rain. West-coast beaches such as Bang Tao, Surin and Kamala face the open Andaman, and swimming is often unsafe in these months. Cape Yamu, on the east coast, faces sheltered water.
Krabi follows the same pattern with its peak in October. Passenger boats are at greater risk in rough monsoon seas, so check conditions before island crossings.
The Gulf: Koh Samui, Hua Hin and Pattaya
The Gulf has two climates, not one.
Koh Samui sits in the southern Gulf and catches the north-east monsoon. October, November and December together bring about 1,000 mm, half the year's total, with November the peak at about 445 mm. January can still be wet. February to April is the driest stretch, and the middle of the year stays moderate at 100 to 135 mm a month while Phuket is soaked. That makes Koh Samui the natural complement to an Andaman home, and supports a second letting season in July and August.
Hua Hin and Pattaya, on the upper Gulf, are drier throughout. Hua Hin averages just 936 mm a year. Only October exceeds 200 mm, and December to February are almost rainless. Pattaya is similar at 1,106 mm, with September and October the wet months. For dependable weather across twelve months, these are the driest of the resort areas.
The north: Chiang Mai
Chiang Mai has a true cool season. From November to January, average lows are 16 to 20°C and highs about 30°C, with almost no rain. It then heats quickly: April averages a daily high of 36.7°C. Rain falls from May to October, peaking in August at about 223 mm.
The drawback is the burning season. From roughly February to April, smoke from crop burning, forest fires and land clearing across northern Thailand and neighbouring countries collects in the mountain valleys. On 16 April 2026 Chiang Mai's air quality index passed 150, in the unhealthy range, and the city was among the ten most polluted major cities in the world. Relief comes only with consistent rain. Bangkok also has high air pollution at times.
Driest and wettest months by area
| Area | Driest months | Wettest months |
|---|---|---|
| Phuket and Krabi | December to March | September and October |
| Koh Samui | February to April | October to December |
| Hua Hin and Pattaya | December to February | September and October |
| Chiang Mai | November to February, with smoke from February to April | August and September |
What this means for buyers
For your own use. Match the dry season to the months you can be there. A family tied to European summer holidays will find Phuket at its wettest in July and August, and Koh Samui or Hua Hin a better fit.
For rental income. Occupancy and nightly rates follow the weather, so an Andaman property earns most of its income in the dry months. Ask any developer or manager for monthly, not annual, occupancy figures. See rental yields in Thailand.
For the building. Humidity and salt air are hard on finishes, air conditioning and pools. Ask how a property is cared for through the wet season when it is empty.
Our seasons tool shows each area by month, and the area matchmaker can weight weather against your other priorities. For the wider comparison, read where to buy in Thailand.
