Jellyfish season in Thailand by month
Jellyfish occur in Thailand all year, but each coast has its own seasons. On the Andaman coast (Phuket, Krabi, Khao Lak) bluebottles arrive with the south-west monsoon, roughly May to October, while other jellyfish are more common in the dry season. In the Gulf of Thailand (Samui, Phangan, Pattaya, Hua Hin) each area has its own peak. The month-by-month level is in the strips below.
Jellyfish occur in Thailand all year, but in different months on different coasts. The Andaman Sea (Phuket, Krabi, Khao Lak) follows the south-west monsoon, the Gulf of Thailand (Samui, Phangan, Pattaya, Hua Hin) the north-east monsoon. Below is the typical risk by month, computed from 2022–2026 weather, official warnings and beachgoer observations.
Andaman Sea
- January: Usually moderate risk. High risk on 3% of days. Onshore wind on 25% of days. Official warnings: 0. Eyewitness reports: 461.
- February: Usually moderate risk. High risk on 5% of days. Onshore wind on 29% of days. Official warnings: 4. Eyewitness reports: 360.
- March: Usually moderate risk. High risk on 3% of days. Onshore wind on 35% of days. Official warnings: 4. Eyewitness reports: 485.
- April: Usually moderate risk. High risk on 21% of days. Onshore wind on 55% of days. Official warnings: 1. Eyewitness reports: 361.
- May: Usually moderate risk. High risk on 26% of days. Onshore wind on 62% of days. Official warnings: 4. Eyewitness reports: 136.
- June: Usually moderate risk. High risk on 14% of days. Onshore wind on 75% of days. Official warnings: 7. Eyewitness reports: 263.
- July: Usually moderate risk. High risk on 6% of days. Onshore wind on 76% of days. Official warnings: 2. Eyewitness reports: 111.
- August: Usually moderate risk. High risk on 9% of days. Onshore wind on 77% of days. Official warnings: 1. Eyewitness reports: 77.
- September: Usually moderate risk. High risk on 6% of days. Onshore wind on 76% of days. Official warnings: 3. Eyewitness reports: 189.
- October: Usually moderate risk. High risk on 2% of days. Onshore wind on 57% of days. Official warnings: 0. Eyewitness reports: 121.
- November: Usually moderate risk. High risk on 0% of days. Onshore wind on 36% of days. Official warnings: 0. Eyewitness reports: 84.
- December: Usually low risk. High risk on 1% of days. Onshore wind on 25% of days. Official warnings: 1. Eyewitness reports: 175.
- 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.
Gulf of Thailand
- January: Usually moderate risk. High risk on 0% of days. Onshore wind on 56% of days. Official warnings: 5. Eyewitness reports: 76.
- February: Usually moderate risk. High risk on 8% of days. Onshore wind on 60% of days. Official warnings: 3. Eyewitness reports: 217.
- March: Usually moderate risk. High risk on 13% of days. Onshore wind on 61% of days. Official warnings: 1. Eyewitness reports: 157.
- April: Usually moderate risk. High risk on 2% of days. Onshore wind on 59% of days. Official warnings: 1. Eyewitness reports: 79.
- May: Usually moderate risk. High risk on 0% of days. Onshore wind on 51% of days. Official warnings: 0. Eyewitness reports: 53.
- June: Usually moderate risk. High risk on 9% of days. Onshore wind on 50% of days. Official warnings: 0. Eyewitness reports: 171.
- July: Usually moderate risk. High risk on 25% of days. Onshore wind on 49% of days. Official warnings: 4. Eyewitness reports: 226.
- August: Usually moderate risk. High risk on 23% of days. Onshore wind on 49% of days. Official warnings: 1. Eyewitness reports: 317.
- September: Usually moderate risk. High risk on 11% of days. Onshore wind on 47% of days. Official warnings: 0. Eyewitness reports: 215.
- October: Usually moderate risk. High risk on 13% of days. Onshore wind on 41% of days. Official warnings: 0. Eyewitness reports: 273.
- November: Usually moderate risk. High risk on 2% of days. Onshore wind on 44% of days. Official warnings: 0. Eyewitness reports: 101.
- December: Usually low risk. High risk on 1% of days. Onshore wind on 49% of days. Official warnings: 0. Eyewitness reports: 66.
- 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.
Phuket has two jellyfish seasons
June–September, south-west monsoon
Onshore wind pushes bluebottles (Portuguese man o’ war) onto the beaches, especially on the exposed west coast after several days of steady westerly wind.
January–April, dry season
Beachgoers most often report other jellyfish: large rhizostome jellyfish, lilac medusae and stinging plankton. The peak is in January, with a second wave in March in some years. The sea is calm then, and stinging plankton shows up as a prickling of the skin in the water.
How the risk level is calculated →
Typical risk by month
Each cell is the typical risk level in that month based on past weather. Tap an area or month for details.
LowModerateHighVery high
Two coasts, two seasons
Andaman Sea: bluebottles (Portuguese man o’ war) are mostly pushed ashore by steady onshore wind during the south-west monsoon, roughly May to October.
Gulf of Thailand: on the eastern and southern Gulf the wind blows onshore in winter (north-east monsoon); box jellyfish occur around Samui, Phangan and Trat in different months, more often in calm weather.
Questions and answers
When is jellyfish season in Phuket?
The risk is most often elevated in May, June, July.
When is jellyfish season in Koh Samui?
The risk is most often elevated in February, March, August.
When is jellyfish season in Pattaya?
The risk is most often elevated in June, July, August.
What should I do if a jellyfish stings me in Thailand?
Get out of the water. Call 1669 for trouble breathing, chest pain or collapse. Do not rub the sting and do not rinse it with fresh water. If a box jellyfish is possible, pour vinegar over the sting for at least 30 seconds.