The driest resort coast in Hawaii on the west — one of the wettest places on earth on the east. Two completely different swimming experiences on one island.
The Big Island has the most extreme climate contrast of any Hawaiian island. The Kohala and Kona coast on the west side receives just 8 to 10 inches of rain per year — making it one of the driest places in Hawaii. Resort beaches like Hapuna, Mauna Kea, and Mauna Lani consistently have some of the cleanest water in the state.
The Hilo side on the east coast is a completely different world. It receives over 130 inches of rain per year, making it one of the wettest places on earth. Brown water advisories on the Big Island almost always affect the east coast. Multiple streams and rivers discharge into the nearshore waters around Hilo, carrying sediment and pollutants after every major rain event.
The notable exception on the west side is Kahalu'u Beach Park in Kona, which has confirmed cesspool contamination from the surrounding residential neighborhood. Bacteria levels at Kahalu'u are frequently elevated regardless of weather — this is a chronic infrastructure problem, not a rain event issue.
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⚠️ Important Disclaimer
Safe to Swim Hawaii is an independent passion project — it is not affiliated with the Hawaii Department of Health or any government agency. Water quality ratings on this site are estimates based on publicly available testing data and geographic analysis. They are not real-time measurements and may not reflect current conditions. “No DOH Alerts” means no advisory is currently posted — it does not mean the water was tested and found safe. DOH only monitors a fraction of Hawaii’s beaches, and some areas have no regular testing at all.
Always verify current water quality conditions with the Hawaii Department of Health Clean Water Branch before entering the water. This site is for informational purposes only and should not be the sole basis for any swimming decisions.
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When in doubt, don't go out. 🤙