When is Hawaii's water warmest? Monthly ocean temps for Oʻahu, Maui, Kauaʻi, and the Big Island — so you can plan the perfect swim.
Hawaii's ocean water is warm year-round — never freezing, never scalding. The range is roughly 73°F in winter to 82°F in late summer. Most visitors don't need a wetsuit; a rash guard for sun protection is more important than thermal protection.
The biggest factors affecting how the water feels: which side of the island you're on (leeward/south-facing bays run warmer), whether it's rained recently (freshwater runoff cools surface temps), and what the surf is doing (churned-up water feels cooler than calm water).
Data based on NOAA buoy averages. Individual beaches vary by 1–3°F depending on exposure, depth, and conditions.
Waikiki and the south shore run slightly warmer than the north shore. In winter, North Shore swells bring colder, deeper water to the surface, so spots like Sunset Beach and Ehukai feel a couple degrees cooler than Waikiki at the same time of year. Waikiki usually stays in the 76–82°F range year-round.
The west side (Kaʻanapali, Kapalua, Napili) and south side (Wailea, Makena) are sheltered and tend to feel warm. The north shore near Hoʻokipa can feel noticeably cooler, especially on windy days. Summer temperatures on Maui's west side regularly hit 80–84°F in calm, shallow bays.
Kauaʻi's north shore (Hanalei, Keʻe) tends to run a touch cooler than the south side (Poʻipū, Salt Pond). Winter north swells bring colder water up from depth. Poʻipū Beach often stays comfortable into November and December due to its southern exposure and protected bay shape.
The Kona and Kohala coasts (west side) are often the warmest swimming waters in all of Hawaii. Protected bays like Kaunaʻoa (Mauna Kea Beach), Hapūna, and Kua Bay are remarkably calm and warm. The Hilo side is wetter, rougher, and tends to run cooler. South Point area has cold upwelling currents from the deep ocean.
Water temps drop into the 73–76°F range. Still comfortable for most adults, but you might want a rash guard for longer snorkel sessions. The upside? Winter is when North Shore waves peak on Oʻahu and Maui, making it spectacular for watching (not swimming). South shores stay calmer and warmer than north shores.
Hawaii also gets its rainy season in winter — heavier rainfall means more brown water runoff events. Always check water clarity before swimming after rain.
Peak water temps hit 80–82°F, sometimes even warmer in shallow, calm bays. North shores are at their calmest and best for swimming. Fewer rainy days means clearer water overall. This is prime season for snorkeling visibility and comfortable snorkel time without a wetsuit.
Watch for jellyfish in late summer — box jellyfish show up roughly 8–10 days after each full moon on Oʻahu's south-facing beaches. Check our Hawaii jellyfish calendar before you go.
Some of the best times to visit. Crowds are lower, prices are better, and water temps are still very comfortable in the 76–80°F range. April and May see warming water after winter, while October the water is still holding onto summer warmth but winter storms haven't arrived yet.
Most swimmers: No. Hawaii's ocean temperatures are warm enough year-round that a wetsuit isn't needed for casual swimming or snorkeling. However:
See our Hawaii rash guard guide for recommendations on sun protection gear.
Ocean temperature only tells you how warm the water feels — not whether it's safe to swim. After heavy rain, water quality can drop sharply even when temperatures are perfect. Always check for brown water advisories and the Hawaii DOH Clean Water Branch before entering the water.
Free alerts when water quality changes at your beach — brown water advisories, bacteria warnings, and all-clear notices.
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Live water quality status across all islands
⚠️ Important Disclaimer
Safe to Swim Hawaii is an independent passion project — not affiliated with the Hawaii Department of Health or any government agency. Temperature data presented here is based on NOAA buoy averages and should be used as a general guide only. Actual conditions vary by beach, depth, time of day, and current weather patterns.
Always verify current water quality conditions with the Hawaii Department of Health Clean Water Branch before entering the water.
When in doubt, don't go out.