Photo: Dibakar Roy / Pexels
Thailand is in for a wet few days. The Thai Meteorological Department (TMD) forecasts heavy rain in 19 provinces today (20 October 2026), with the East and South seeing continuous, locally very heavy downpours. The Andaman coast, which includes Krabi and so Koh Lanta, is expecting thundershowers, isolated heavy rain and waves above 2 m in storms. Rainfall is expected to increase further from 21 to 25 October, so it's worth building some buffer into your plans.
What's driving the rain
A monsoon trough is sitting across the Gulf of Thailand and the middle of the South. At the same time, a high-pressure system from China covers the upper North, the upper Northeast and the South China Sea. Together they push easterly winds across Thailand and the Gulf, which is fuelling the rain.
For comparison, 18 October had heavy rain in 14 provinces (with showers in Bangkok), and 19 October had heavy rain in 27 provinces (with heavy rain in Bangkok).
What it means for Koh Lanta and the Andaman coast
The forecast doesn't name Koh Lanta specifically. Krabi falls in the west-coast South zone, which is the one that applies to us:
- Fairly widespread thundershowers
- Isolated heavy rain in Ranong, Phang Nga, Phuket and Krabi
- Isolated very heavy rain in Trang and Satun
- Temperatures of 23-24°C at night and 30-33°C during the day
- Winds of 15-30 km/h
- Waves of 1-2 m, going above 2 m in thundershowers
Boats and ferries
Waves in the South are 1-2 m on both coasts, and above 2 m in thundershowers. Winds of 15-30 km/h add to that. The TMD advises ships in the Andaman Sea and the Gulf to avoid thundershowers. If you have a boat trip or island ferry booked, check with your operator and expect possible disruption.
In the East, waves are under 1 m but go above 2 m in thundershowers.
Flood and landslide warnings
The TMD warns of gusty winds and heavy to very heavy rain. There is a risk of flash floods, overflows and landslides, highest near foothills and waterways, though lowlands can be affected too. Steer clear of river and foothill areas while the rain lasts.
Southern provinces with very heavy rain
Seven southern provinces are forecast to get very heavy rain: Chumphon, Nakhon Si Thammarat, Phatthalung, Songkhla, Surat Thani, Satun and Trang.
Surat Thani is on the Gulf side, so the Samui area is included in that forecast.
Forecast by region
| Region | Conditions | Low / High (°C) | Wind |
|---|---|---|---|
| Bangkok | Scattered thundershowers | 25-27 / 32-35 | NE 10-20 km/h |
| North | Isolated thundershowers, mostly Mae Hong Son, Tak | 21-25 / 34-35 | NE 10-20 km/h |
| Northeast | Isolated thundershowers, mostly Nakhon Ratchasima, Buriram, Surin. Scattered storms in Si Sa Ket, Ubon Ratchathani | 22-24 / 33-35 | NE 10-20 km/h |
| Central | Scattered thundershowers, mostly Ayutthaya, Suphan Buri, Kanchanaburi, Ratchaburi, Nakhon Pathom, Samut Sakhon, Samut Songkhram | 24-26 / 33-35 | NE 10-20 km/h |
| East | Scattered thundershowers, isolated heavy rain in Chon Buri, Rayong, Chanthaburi, Trat | 23-26 / 33-34 | 10-30 km/h |
| South, east coast | Fairly widespread thundershowers, isolated heavy rain in Phetchaburi, Prachuap Khiri Khan, Pattani, Narathiwat. Isolated very heavy rain in Chumphon, Surat Thani, Nakhon Si Thammarat, Phatthalung, Songkhla | 23-24 / 31-33 | 15-30 km/h |
| South, west coast (Andaman) | Fairly widespread thundershowers, isolated heavy rain in Ranong, Phang Nga, Phuket, Krabi. Isolated very heavy rain in Trang, Satun | 23-24 / 30-33 | 15-30 km/h |
Travelling elsewhere in Thailand
- Bangkok: Mostly manageable, with scattered showers and heat of 32-35°C.
- North and Northeast: Comparatively dry, with only isolated storms.
- 21-25 October: Rainfall is expected to increase, hitting the lower Northeast, the Central region, the East and the upper South hardest. If you're travelling through those areas, allow extra time.
Information sourced from The Thaiger.