About the data and the risk estimate

What we do

Jellymeter is a research-driven service that estimates the risk of meeting jellyfish on Thai beaches. We combine official warnings, wind, wave and current data, the history of past cases and reports from beachgoers into a clear forecast for every beach.

The model is described openly on the sources and methodology page, and we check its accuracy against past data.

What the map shows

For each beach we estimate how likely you are to meet jellyfish today and for the next 5 days: low, moderate, high or very high.

It is an estimate, not a safety guarantee. "No reports" only means nobody has reported jellyfish, not that there are none. Always check beach flags and follow lifeguards.

Sources

Official warnings from Thailand’s Department of Marine and Coastal Resources (DMCR, warning.dmcr.go.th), checked every 3 hours.

Wind, rain, wave and sea-temperature forecasts from Open-Meteo, refreshed every 6 hours.

Reports from beachgoers on this site, both "jellyfish seen" and "no jellyfish". A moderator hides spam and marks reports as verified.

How the risk is estimated

Season: the Andaman Sea and the Gulf of Thailand have different jellyfish seasons, so the baseline depends on the coast and the month.

Onshore wind and waves: steady wind and swell toward the shore over the past two to three days push bluebottles onto beaches, in summer on the Andaman coast and in winter on parts of the Gulf.

Calm sea and rain: box jellyfish are more common in calm, shallow water, especially after heavy rain.

Reports: official and verified reports raise the risk at the beach and, less, at nearby beaches; their weight halves every few days. "No jellyfish" reports lower the estimate slightly.

Each beach page has a "Why this level" block showing what the estimate is made of.

Limitations

Official warnings are rare, typically 15–20 a year for the whole country, and not every incident is reported.

Weather forecasts for individual bays can differ from real conditions.

Beachgoer reports are not checked on site; unverified reports carry less weight.

Telegram bot

The Telegram bot sends alerts when the risk at your beaches turns high or a new warning appears.