Jellyfish at Siam Bay (Koh Racha Yai)

อ่าวสยาม · Phuket · Andaman Sea

Risk today · 25 Oct 2026Moderate

Main factor: Steady onshore wind for 5 days

Conditions or reports nearby make an encounter more likely.

Today the jellyfish risk at Siam Bay (Koh Racha Yai) Beach is moderate. Main factor: steady onshore wind for 5 days. In October it is usually moderate here. It is an estimate, not a guarantee: follow beach flags and lifeguards.

What to expect today

5-day outlook

  1. TodayModerate8 m/s W — Wind: up to 8 m/s, blowing from W. The arrow shows where it blows to. Onshore wind pushes jellyfish to the beach.0.8 m — Waves: up to 0.8 m during the day. Strong onshore waves wash jellyfish ashore; box jellyfish prefer calm water.26 mm — Rain: 26 mm in the day. Box jellyfish are more common near river mouths after heavy rain.
  2. TomorrowModerate5 m/s W — Wind: up to 5 m/s, blowing from W. The arrow shows where it blows to. Onshore wind pushes jellyfish to the beach.1.0 m — Waves: up to 1.0 m during the day. Strong onshore waves wash jellyfish ashore; box jellyfish prefer calm water.30 mm — Rain: 30 mm in the day. Box jellyfish are more common near river mouths after heavy rain.
  3. Tue 27Moderate6 m/s W — Wind: up to 6 m/s, blowing from W. The arrow shows where it blows to. Onshore wind pushes jellyfish to the beach.0.9 m — Waves: up to 0.9 m during the day. Strong onshore waves wash jellyfish ashore; box jellyfish prefer calm water.44 mm — Rain: 44 mm in the day. Box jellyfish are more common near river mouths after heavy rain.
  4. Wed 28Moderate6 m/s S — Wind: up to 6 m/s, blowing from S. The arrow shows where it blows to. Onshore wind pushes jellyfish to the beach.0.5 m — Waves: up to 0.5 m during the day. Strong onshore waves wash jellyfish ashore; box jellyfish prefer calm water.24 mm — Rain: 24 mm in the day. Box jellyfish are more common near river mouths after heavy rain.
  5. Thu 29Moderate6 m/s SE — Wind: up to 6 m/s, blowing from SE. The arrow shows where it blows to. Onshore wind pushes jellyfish to the beach.0.5 m — Waves: up to 0.5 m during the day. Strong onshore waves wash jellyfish ashore; box jellyfish prefer calm water.23 mm — Rain: 23 mm in the day. Box jellyfish are more common near river mouths after heavy rain.
  6. Fri 30Moderate7 m/s SE — Wind: up to 7 m/s, blowing from SE. The arrow shows where it blows to. Onshore wind pushes jellyfish to the beach.0.5 m — Waves: up to 0.5 m during the day. Strong onshore waves wash jellyfish ashore; box jellyfish prefer calm water.25 mm — Rain: 25 mm in the day. Box jellyfish are more common near river mouths after heavy rain.

Why this level

  • Bluebottles (Portuguese man o’ war) Moderateraises risk
    above usual for the season · steady onshore wind for 5 days · calm sea
  • Other jellyfish and stinging plankton Lowusual background
    jellyfish season in this area, usual for the season
  • Box jellyfish Lowlowers risk
    below usual for the season

It is not jellyfish season in Phuket, the wind blows from the sea (~2.3 m/s), stronger than usual, the wind has blown from the sea for 5 days in a row, which is how bluebottles usually arrive, moderate waves (~0.8 m), so the risk level is moderate. There are no recent jellyfish reports.

Recent reports

No recent reports.

Report jellyfish

At this beach now? Your report helps others. "No jellyfish today" is useful too.

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Seasonality

Bars show the baseline seasonal risk for this coast; dots show official warnings nearby by month.

Siam Bay (Koh Racha Yai): jellyfish month by month

  1. January: Usually moderate risk. High risk on 4% of days. Onshore wind on 93% of days. Official warnings: 0.
  2. February: Usually moderate risk. High risk on 17% of days. Onshore wind on 91% of days. Official warnings: 0.
  3. March: Usually moderate risk. High risk on 3% of days. Onshore wind on 87% of days. Official warnings: 1. Eyewitness reports: 3.
  4. April: Usually moderate risk. High risk on 3% of days. Onshore wind on 76% of days. Official warnings: 0. Eyewitness reports: 20.
  5. May: Usually moderate risk. High risk on 19% of days. Onshore wind on 60% of days. Official warnings: 1.
  6. June: Usually moderate risk. High risk on 27% of days. Onshore wind on 47% of days. Official warnings: 1.
  7. July: Usually moderate risk. High risk on 24% of days. Onshore wind on 39% of days. Official warnings: 0.
  8. August: Usually moderate risk. High risk on 30% of days. Onshore wind on 50% of days. Official warnings: 0.
  9. September: Usually moderate risk. High risk on 11% of days. Onshore wind on 57% of days. Official warnings: 1.
  10. October: Usually moderate risk. High risk on 3% of days. Onshore wind on 82% of days. Official warnings: 0.
  11. November: Usually moderate risk. High risk on 0% of days. Onshore wind on 98% of days. Official warnings: 0.
  12. December: Usually moderate risk. High risk on 1% of days. Onshore wind on 99% of days. Official warnings: 0.
  • Low
  • Moderate
  • High
  • Very high

Colour shows the typical risk level that month; the number is the share of high-risk days. Warnings and sightings are in each month’s tooltip.

Coordinates: 7.6112, 98.3703

Questions and answers

Can I swim at Siam Bay (Koh Racha Yai) today?

Today's estimated risk is moderate; main factor: steady onshore wind for 5 days. It is an estimate, not a guarantee: "no reports" does not mean there are no jellyfish. Check beach flags and follow lifeguards.

Have jellyfish been seen at Siam Bay (Koh Racha Yai) recently?

No reports in the last 14 days. It is an estimate, not a guarantee: "no reports" does not mean there are no jellyfish. Check beach flags and follow lifeguards.

In which months are jellyfish more likely at Siam Bay (Koh Racha Yai)?

Based on 2022–2026 weather, the risk is most often elevated in June, July, August. Official warnings nearby: 4.

Who do I call after a jellyfish sting?

Emergency medical services in Thailand: 1669 (free). Alert the beach lifeguard; if a box jellyfish is possible, pour vinegar over the sting for at least 30 seconds.