Month-by-month ocean temperatures, best swimming months, and jellyfish seasons
Waikiki’s ocean water is warm enough to swim in comfortably year-round. Water temperatures hover between 74°F in winter and 82°F in late summer — a remarkably narrow range compared to mainland beaches. You won’t need a wetsuit at any time of year unless you’re doing extended snorkeling sessions.
NOAA’s tide gauge at Honolulu Harbor provides continuous sea surface temperature data for the Waikiki area. The figures below are derived from long-term NOAA averages and reflect typical conditions — actual temperatures on any given day may vary slightly.
Based on NOAA long-term averages for Honolulu Harbor. Individual days vary.
Ocean temps peak at 81–82°F. Hurricane season runs through November, but direct impacts on Oʻahu are rare. The tail end of summer brings warm, calm water with typically excellent conditions.
Water warming rapidly (77–79°F), dry season kicking in, crowds lighter than peak summer, and fewer jellyfish events relative to fall. Locals often cite this as their favorite swimming season.
Water at its coolest (74–75°F) but still perfectly swimmable. More rain increases advisory risk. Worth wearing a rash guard for longer sessions. Whale watching is spectacular from Waikiki in January–March.
Box jellyfish wash onto Waikiki’s south-facing beach approximately 8–10 days after every full moon. The cycle is predictable enough that the City & County of Honolulu Ocean Safety posts forecast warnings. The influx typically lasts 2–3 days then subsides.
This happens year-round — no season is "jellyfish-free." The months with the most intense influxes tend to be when ocean currents are strongest. Wearing a full rash guard significantly reduces your exposed skin area.
Bluebottles/man-o-war appear when northeast trade winds are strong, blowing them onto windward and south-facing shores. Most common in winter and spring. Watch for blue bubble-like objects on the waterline and ask lifeguards about current conditions. Warning flags are posted on the beach when man-o-war are present.
Waikiki sits adjacent to the Ala Wai Canal, which drains urban Honolulu’s runoff. After heavy rain, bacteria levels can spike significantly. Check current advisory status at safetoswimhawaii.com before swimming, especially after any significant rainfall.
During dry conditions, Waikiki’s water quality is typically adequate for swimming at most sites. The DOH monitors multiple Waikiki sites regularly. The cleanest water within Waikiki is generally found toward the Diamond Head end of the beach (away from the Ala Wai Canal outfall). For consistently cleaner water on Oʻahu, consider Ko Olina, Kailua, or Lanikai — beaches that sit away from urban runoff corridors.
Free alerts for Waikiki water quality advisories, jellyfish warnings, and beach conditions. Know before you go.
No spam. Just safety alerts for your trip.
⚠️ Important Disclaimer
Safe to Swim Hawaii is an independent passion project — not affiliated with DOH or any government agency. Temperature data represents long-term NOAA averages and is not real-time.
Always verify conditions with the Hawaii DOH Clean Water Branch before entering the water.
When in doubt, don't go out. 🤙