Jellyfish Arrival Calendar – Jellyfish Forecast for Hawaii Beaches

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 (pluck, not scrape) the tentacles from the skin (use a towel, napkin, or other item other than your fingers) and rinse the affected area with vinegar.

2. 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.

A team of University of Hawaii researchers recently published a report in the journal Toxins about the best treatment for box jellyfish stings. According to the researchers, vinegar is effective in preventing more venom from being released into the skin, as is a product called Sting No More, which has a venon-inhibiting effect. A hot water compress can be used to treat the sting's effects. The report comes to the conclusion that seawater, soda, urine, alcohol and ethanol had no effect, and that freshwater poured over a sting or icing the area could make things worse.

Jellyfish Info

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.