El Nino Watch
The Thai Meteorological Department grades 24-hour rain as light (0.1-10 mm), moderate (10.1-35), heavy (35.1-90) and very heavy (more than 90 mm).
Hazards
1 mm of rain = 1 litre of water per square metre. The TMD classes (rain over 24 hours, 07:00 to 07:00) are in the table.
For scale: a very heavy day can bring more rain than Samui normally gets in the whole month of February (about 39 mm in the ERA5 1991-2020 normal).
| Class (TMD) | Rain in 24 h |
|---|---|
| Light rain | 0.1 to 10.0 mm |
| Moderate rain | 10.1 to 35.0 mm |
| Heavy rain | 35.1 to 90.0 mm |
| Very heavy rain | 90.1 mm or more |