El Nino Watch
Scores how strong El Nino is, from the latest ONI and weekly Nino 3.4. It can raise the overall level to Prepare but never higher: it is a warning sign, not a direct threat.
Koh Samui watch
The factor takes the higher of two levels: one from the latest ONI and one from the latest weekly Nino 3.4 anomaly. The explanation also shows the NOAA alert status and the highest El Nino probability in the IRI forecast (for context; they do not change the level).
It is marked stale if the newest ONI is more than 120 days old.
A strong El Nino usually means below-normal rain and a hotter, longer dry season in Thailand. For Samui, the water risk window is February-April 2027.
| Value (ONI or weekly Nino 3.4) | Factor level |
|---|---|
| below +0.5 °C | 0 Normal |
| +0.5 to +1.49 °C (weak or moderate El Nino) | 1 Watch |
| +1.5 °C or more (strong, and very strong) | 2 Prepare |
Cap in the overall level: 2. Critical factor.