South shore arrival predictions based on lunar cycle
No Jellyfish Warning
Next warning window begins April 9. Next full moon: May 1.
Box jellyfish arrive on Hawaii's shores in a predictable pattern tied to the lunar cycle. Approximately 8 to 10 days after each full moon, ocean currents push them toward south-facing shores — particularly Waikiki, Ala Moana Beach Park, and Hanauma Bay on Oʻahu. This pattern has been documented over decades by Ocean Safety lifeguards and marine researchers.
While south-facing shores see the highest concentrations, box jellyfish can appear on any shore depending on wind and current conditions. They belong to the invertebrate Phylum Cnidaria and are named for the squarish shape of their bell-shaped body.
If Stung
Current research recommends rinsing with vinegar to neutralize stinging cells, then applying heat (hot water or hot packs at 40–45°C) for pain relief. Do not rinse with fresh water or rub with sand.
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 signs posted on beaches. Swim on guarded beaches only and ask a lifeguard about the presence of jellyfish and other ocean hazards.