North shore to south shore: a 10x rainfall difference and completely different water quality.
The Hawaii Department of Health recommends staying out of the ocean for at least 72 hours after heavy rain. Kauaʻi has the most extreme rainfall gradient of any Hawaiian island. Mt. Waiʻaleʻale averages 450 inches per year, while Poipu gets 30. Choose your coast accordingly.
Rainfall: ~30 in/yr
Character: Dry, sunny, family-friendly. Primary resort area.
Water quality: Consistently the best on the island.
Key beaches: Poipu Beach, Brenneckeʻs, Shipwreck Beach. Full guide →
Rainfall: 80-100+ in/yr (Mt. Waiʻaleʻale: 450 in/yr)
Character: Dramatic, lush, wet. World-famous beauty. Nā Pali Coast.
Water quality: Hanalei Bay impaired since 2004. High rainfall = frequent runoff events.
Key beaches: Hanalei Bay, Tunnels (Makua), Keʻe Beach, Anini Beach. Full guide →
Rainfall: 40-60 in/yr
Character: Main town area (Kapaʻa, Līhuʻe). Airport is here (LIH). Mix of local and tourist.
Water quality: Moderate. Wailua River mouth can affect nearby beaches. Lydgate Beach Park has a protected pool.
Key beaches: Lydgate Beach, Kapaʻa Beach, Kealia Beach
Rainfall: 20-30 in/yr
Character: Dry, remote, local. Gateway to Waimea Canyon. Polihale State Park is one of Hawaiʻiʻs longest, most remote beaches.
Water quality: Generally good due to dry climate. Waimea River mouth can have issues.
Key beaches: Salt Pond Beach, Polihale Beach (remote, 4WD recommended)
Top-rated experiences in the area.
Tours via Viator and GetYourGuide. We may earn a commission at no extra cost to you.
Free alerts when water quality changes.
No spam. Just safety alerts.
100+ beaches 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. 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. 🤙