What to expect for water quality, rainfall, and ocean conditions
Hanalei Bay's water quality is severely impacted by the 360+ cesspools in its watershed. Any significant rain event pushes untreated sewage through the four rivers into the bay. The EPA lists this bay as impaired.
October marks a significant shift at Hanalei with 5-6 inches of rain. North swells arrive, creating large surf. The four rivers begin swelling with runoff. Cesspool saturation increases. Water quality at river mouths deteriorates quickly.
Winter north swells transform Hanalei Bay into a powerful surf zone. Waves regularly exceed 10-15 feet. The bay is extremely dangerous for swimming during big swell events. Strong currents develop near the pier and river mouths.
Moderate to low. Fall shoulder season offers fewer tourists while conditions remain good. This is one of the best value periods for visiting Hawaii.
The Hawaii Department of Health recommends staying out of the ocean for at least 72 hours after heavy rain. In october, this is especially important as wet-season storms can produce heavy rainfall and significant runoff.
When conditions are clear, Hanalei Bay has excellent ocean activities. Check the water quality above, then book with confidence.
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Safe to Swim Hawaii provides water quality information based on publicly available DOH data and seasonal patterns. This is not medical or safety advice. Always check current conditions, obey posted signs, and use your own judgment before entering the ocean. Privacy Policy
⚠️ Important Disclaimer
Safe to Swim Hawaii is an independent passion project — not affiliated with the Hawaii Department of Health or any government agency. Water quality ratings are estimates based on publicly available testing data and geographic analysis. They are not real-time measurements and may not reflect current conditions.
Always verify current water quality conditions with the Hawaii DOH Clean Water Branch before entering the water.
When in doubt, don't go out. 🤙