Box Jellyfish in Hawaii — When They Show Up (2026 Calendar)

One of the more useful pieces of locals-only knowledge in Hawaii: **box jellyfish show up on a predictable schedule.** They're drawn into south-shore beaches **8 to 12 days after every full moon.** It's not magic — they're responding to lunar tides and a wind pattern that pushes them inshore. ## 2026 box jellyfish window calendar (Honolulu / South Shore) | Full Moon (2026) | Likely jellyfish window | |---|---| | Jan 4 | Jan 12–16 | | Feb 3 | Feb 11–15 | | Mar 4 | Mar 12–16 | | Apr 3 | Apr 11–15 | | May 2 | May 10–14 | | Jun 1 | Jun 9–13 | | Jul 1 | Jul 9–13 | | Jul 30 | Aug 7–11 | | Aug 28 | Sep 5–9 | | Sep 27 | Oct 5–9 | | Oct 26 | Nov 3–7 | | Nov 25 | Dec 3–7 | | Dec 24 | Jan 1–5 (2027) | **Note:** Verify dates with the [Waikīkī Aquarium box jellyfish calendar](https://waikikiaquarium.org) which is updated continuously and considered the official local source. ## Where they show up Mostly **south-facing Oʻahu beaches**: - Waikīkī (most affected) - Ala Moana Beach Park - Hanauma Bay (occasionally) - Sandy Beach (rarely) - Magic Island North and east shores rarely see them. Other islands have box jellyfish too but in lower density. ## What they look like Small — 1 to 3 inches across the bell, transparent with four tentacles trailing 2–3 feet. They're nearly invisible in the water. Lifeguards often post signs at high-risk windows but always check the sign at the beach before swimming. ## If you get stung 1. **Get out of the water.** Don't panic. 2. **Don't rub the area** — it makes more nematocysts fire. 3. **Rinse with sea water** (NOT fresh water — fresh water triggers more stings). 4. **Apply white vinegar for 30 seconds** if available. Most Waikīkī beach showers have vinegar dispensers now. 5. **Remove any visible tentacles** with the edge of a credit card or sand-covered hand (gloves if possible). 6. **Heat helps.** Hot pack or hot shower (110°F) for 30+ minutes. 7. **See a lifeguard.** Most Waikīkī beaches have one within walking distance. Severe sting (large area covered, difficulty breathing, chest pain): **call 911 immediately.** Hawaii box jellyfish stings are painful but rarely life-threatening — but allergic reactions can be. ## Common myths - **"Pee on it":** Bad advice. Doesn't help and may worsen. - **"Wear pantyhose":** This actually works for blocking nematocysts but is rarely practical. - **"Stay out the whole window":** Many locals swim during box jellyfish windows by checking signs and avoiding mornings (worst time). ## What about Portuguese man-of-war? Different animal — bluish balloon with a long blue tentacle. Driven onshore by trade winds, not lunar cycles. **Treatment is the same** (vinegar, heat, lifeguard). ## See current Hawaii beach events We don't list "jellyfish" as an event but we do track beach cleanups, surf contests, ocean safety events: **[Browse all Hawaii events →](/events)** **[12 Hidden Beaches in Hawaii →](/blog/hidden-beaches-hawaii-2026)** **[Best Snorkeling Spots in Hawaii →](/blog/best-snorkeling-spots-hawaii-2026)**