Jellyfish Calendar
Box jellyfish warning dates for Hawaii's south-facing beaches — calculated from the lunar cycle.
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Today
Full moon
Upcoming Warning Dates
How It Works
The Pattern
Hawaiian box jellyfish (Alatina alata) follow a predictable cycle tied to the moon. They arrive on south-facing shores approximately 8 to 10 days after each full moon, almost like clockwork.
Which Beaches
South-facing shores are most affected: Waikiki, Ala Moana Beach Park, Hanauma Bay, and Pokāī Bay on Oahu. Maui south shore beaches (Kīhei, Wailea) occasionally see them too. North shores are rarely affected.
If You Get Stung
Rinse with vinegar (not fresh water). Remove tentacles with tweezers or a credit card edge. Apply heat (hot shower or hot pack, not scalding) for 20 minutes. Seek medical attention for severe reactions, difficulty breathing, or stings to the face or chest.
How to Avoid Them
Check this calendar before planning south shore beach days. On warning days, swim at north-facing or west-facing beaches instead. Look for purple warning signs posted by lifeguards at affected beaches.
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