05/20/2026
Plopping this right here for a bookmark that helps everyone🪼
Box jellyfish in Hawaii don't show up randomly. They appear 8–10 days after every full moon, on a predictable schedule that repeats every single month. The next warning window is June 8–10. Then July 7–9. Then August 6–8.
But if you're swimming anywhere on the leeward shores after June 8th, there's a date you need to know before you book your beach day.
The beaches most affected are the calm, clear, beautiful ones on the west and south-facing shores — exactly the ones everyone wants to swim at.
We built a free jellyfish calendar that shows every warning date through the end of the year, plus which beaches to watch. Check it before you plan your beach days this summer.
https://www.hawaii-guide.com/jellyfish-calendar
