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Heavy rain is forecast across Thailand through 25 October, according to a warning the Thai Meteorological Department issued on Sunday 18 October. The department says some areas could see heavy to very heavy downpours, with a risk of flash floods, runoff and landslides. Waves in the Andaman Sea and Gulf of Thailand may exceed 3 metres during thunderstorms, so anyone planning boat trips or travel should keep their schedule flexible.
What the forecast says
The warning covers 18 to 25 October and splits the week into two phases.
| Dates | Where | What to expect |
|---|---|---|
| Sun 18 to Tue 20 Oct | South and East | Continuous rain, with heavy to very heavy downpours in some areas |
| Wed 21 to Sun 25 Oct | Lower Northeast, Central region (including Bangkok and surrounding provinces), East, upper South | Rain intensifies, with heavy to very heavy rain and gusty winds in some areas |
Why it's happening
A monsoon trough over the lower South and the southwest monsoon over the lower Andaman Sea drive the rain at first. The trough is expected to shift north over the central South. Meanwhile, a high-pressure system from China extends over the upper North, upper Northeast and South China Sea.
Sea conditions
Waves in the Andaman Sea and Gulf of Thailand may exceed 3 metres during thunderstorms. The department advises all vessels to proceed with caution and avoid stormy areas.
What it means for Koh Lanta visitors
The article refers to "the South" and the "lower Andaman Sea" for 18 to 20 October. It doesn't name Koh Lanta or Krabi specifically. Southwest monsoon conditions do suggest rough seas and heavy showers along the Andaman coast, so it's sensible to plan around that.
- Boats and ferries: with waves over 3 metres possible during storms, expect cancelled or delayed ferries, speedboats and island tours.
- Beaches: swimming in rough seas is risky.
- Roads: flooding is likely in low-lying areas.
- Onward travel: Bangkok and the Central region get the worst of it from 21 October, which may disrupt flights and ground transport.
Practical tips
- Watch accumulated rainfall, especially in low-lying areas and along waterways near foothills.
- If you're driving or riding, avoid flood-prone routes.
- Allow buffer time for any travel, and check your operator's status on the day.
- Have indoor backup plans ready.
Information sourced from Bangkok Post.