Photo: Roman Castillo / Pexels
Heavy rain is forecast for 15 provinces in Thailand on 21 October 2026, according to the Thai Meteorological Department (TMD). Koh Lanta sits in Krabi province on the Andaman side, where scattered thundershowers and some heavy rain are expected. Highs will reach 33-35°C, waves will be around 1 m and could top 2 m inside storms, and the number of heavy-rain provinces has dropped over the past few days.
What's driving the weather
A monsoon trough is sitting across the Gulf of Thailand and the middle of the South. A high-pressure system from China covers the upper North, the upper Northeast and the South China Sea. Southeasterly winds are carrying moisture from the South China Sea and the Gulf into the lower Northeast, the lower Central region (including Bangkok) and the East.
The South gets continuous rain with isolated heavy falls. The upper parts of the country see isolated thundershowers with gusts.
Krabi and the west coast (including Koh Lanta)
The TMD lists Krabi in the South's west coast group, alongside Ranong, Phang Nga, Phuket, Trang and Satun.
- Conditions: scattered thundershowers, with isolated heavy rain
- Temperatures: lows of 24-25°C, highs of 33-35°C
- Wind: easterly at 15-30 km/h from Ranong northward, and southwesterly at 15-30 km/h from Phang Nga southward
That wind is noticeable out on the water.
Sea conditions
Waves on the west coast are about 1 m, but they can exceed 2 m inside thundershowers. Boat trips and island hopping could be rough or cancelled during storms, so check with your operator before you go.
The South's east coast and the East region have similar conditions. The South's east coast has waves of about 1 m, rising above 2 m in thundershowers. In the East, waves are under 1 m, rising above 2 m in thundershowers.
Forecast by region
| Region | Conditions | Min °C | Max °C | Wind |
|---|---|---|---|---|
| Bangkok | Isolated thundershowers with gusts | 26-27 | 33-35 | Southeasterly 10-20 km/h |
| North | Isolated thundershowers, mostly Phitsanulok, Phetchabun, Phichit | 21-25 | 34-36 | Easterly 10-20 km/h |
| Northeast | Isolated thundershowers with gusts, mostly Nakhon Ratchasima, Buriram, Surin, Si Sa Ket, Ubon Ratchathani | 23-24 | 34-35 | Northeasterly 10-20 km/h |
| Central | Isolated thundershowers with gusts, mostly Ayutthaya, Suphan Buri, Kanchanaburi, Ratchaburi, Nakhon Pathom, Samut Sakhon, Samut Songkhram | 23-26 | 32-36 | Easterly 10-20 km/h |
| East | Isolated thundershowers with gusts, mostly Nakhon Nayok, Prachin Buri, Chachoengsao, Chon Buri, Rayong, Chanthaburi, Trat | 23-26 | 32-35 | Southeasterly 10-30 km/h |
| South, east coast | Scattered thundershowers, isolated heavy rain: Prachuap Khiri Khan, Chumphon, Surat Thani, Nakhon Si Thammarat, Phatthalung, Songkhla, Pattani, Yala, Narathiwat | 22-25 | 30-35 | Easterly 15-30 km/h from Surat Thani northward; southeasterly 15-30 km/h from Nakhon Si Thammarat southward |
| South, west coast | Scattered thundershowers, isolated heavy rain: Ranong, Phang Nga, Phuket, Krabi, Trang, Satun | 24-25 | 33-35 | Easterly 15-30 km/h from Ranong northward; southwesterly 15-30 km/h from Phang Nga southward |
If you're heading to Bangkok
Bangkok only has isolated showers and gusts, with temperatures of 26-35°C. Carry a rain cover and expect brief interruptions rather than all-day rain.
The wider pattern
This is the late wet season. Rain is widespread but varies by area, and the northern and eastern regions are drier and hotter, with highs up to 36°C.
The count of heavy-rain provinces has fallen each day. Related Thaiger daily forecasts showed heavy rain in 27 provinces on 19 October (including Bangkok) and in 19 provinces on 20 October.
Limits of the forecast
The source gives no warning levels, no rainfall totals in mm and no named storm. It also doesn't list all 15 heavy-rain provinces.
Information sourced from The Thaiger.