Jellyfish Arrival Calendar – Jellyfish Forecast for Hawaii Beaches
Jellyfish invasion likely Full moon
Note: This calendar is for informational purposes only. All jellyfish arrival dates are estimates. Jellyfish may be present on any day of the year. Always obey warning sings posted on beaches. Swim on guarded beaches only and ask a lifeguard about the presence of jellyfish and other ocean hazards.
Jellyfish First Aid
In case you get stung by a jellyfish or Portuguese man-of-war:
1. Carefully remove and tentacles on the skin (use a towel, napkin, or other item other than your fingers) and rinse the affected area with water or vinegar.
2. Apply ice for pain.
3. Get medical help in case you suffer from a severe reaction. Immediate medical care may be necessary as jellyfish stings may cause an anaphylactic shock or even death. Get the help of a lifeguard or call 911
The most common type of jellyfish in Hawaii is the “Carybdea alata” and “Carybdea rastonii,” also known as “box jellyfish” because of its squared body. The box jellyfish is most commonly found on Hawaii’s leeward (west) and south shores. Their arrival on Hawaii’s beaches is quite predictable. They usually arrive around 9-12 days after a full moon (but occasionally they have been observed on off-cycle days as well). This is when warning signs are usually posted on many Oahu beaches (warning signs are generally only posted on popular beaches).
Don’t swim at remote and unguarded beaches for your own safety. There are many other ocean hazards besides jellyfish, including strong currents, rip tides, sharp coral, etc. Similar to a jellyfish, the Portuguese man-of-war also causes a painful sting. It has a purplish body and is commonly found on windward (east) shores as the prevalent northeastern tradewinds blow these creatures close to shore.
If you see a jellyfish on the beach, don’t touch it as its tentacles can cause a painful sting even if the animal is dead. Keep children away from beached jellyfish. If you get stung, see a lifeguard for first aid. For more serious cases or if you feel unwell, call 911 immediately.