Is it safe to swim today? Check live DOH advisory status — bacteria risk rating, 72-hour rain rule, and Kawainui Marsh drainage
📍 On Oʻahu's windward coast, about 30 minutes over the Pali from Waikiki
Kailua Beach water quality today: This beach carries a moderate 2/5 historical bacteria risk and passes DOH testing most of the time during dry weather. After rain: DOH recommends waiting at least 72 hours. Kawainui Marsh — Hawaii's largest wetland — plus Kaelepulu Stream, Kawainui Canal, and Makawao Stream drain toward the south end, spiking bacteria after storms. If the water looks brown, stay out regardless of what any advisory says. The south end near stream outlets tends to have higher bacteria levels after rain. Check live advisory status above and make your own judgment.
Kailua Beach is a hub for kayaking, paddleboarding, and exploring the windward coast. When the water is clear, these activities are hard to beat.
Tours listed via Viator and GetYourGuide. Safe to Swim Hawaii may earn a commission if you book, at no extra cost to you.
A 2.5-mile stretch of white sand on Oʻahu's windward coast, consistently ranked among the best beaches in America. Known for steady trade winds that make it popular for kayaking, windsurfing, and stand-up paddleboarding. The beach has two distinct sections — the south end near the boat ramp receives more stream runoff, while the north end toward Lanikai tends to have better water quality.
Kailua Beach is a DOH Tier 1 monitored beach that generally passes bacteria testing under normal conditions. However, it sits at the outlet of the Kawainui Marsh system — the largest wetland in Hawaii — which drains through Kaelepulu Stream and Kawainui Canal into Kailua Bay.
After heavy rain, these waterways carry urban runoff, sediment, and potentially elevated bacteria into the nearshore waters. The stream outlets are on the south end of Kailua Beach near the boat ramp. The northern end of the beach (toward Lanikai) tends to be less affected because it is farther from the drainage outlets.
Based on: DOH Tier 1 beach monitoring, Kawainui Marsh drainage proximity, geographic risk assessment
Kailua Beach stretches 2.5 miles along the windward coast. Water quality varies significantly by location because of where the stream outlets are.
Kawainui Canal and Kaelepulu Stream empty into Kailua Bay here. After rain, this is where bacteria concentrates first. The boat ramp area and the channel between the two stream outlets are the most affected zones. Avoid swimming here for 72+ hours after storms.
The main beach area between the stream outlets and the lifeguard tower. Generally passes DOH testing in dry weather. After rain, bacteria can drift north from the south end depending on currents and wind. The beach park facilities are in this zone.
The stretch from the main beach park north toward Lanikai has the cleanest water at Kailua. It is farthest from the stream outlets and benefits from open ocean circulation. Even after moderate rain, this section recovers faster than the south end.
Kawainui Marsh is the largest wetland in Hawaii — 830 acres of marshland that collects rainwater from the Koʻolau mountains and channels it through Kaelepulu Stream and Kawainui Canal into Kailua Bay.
The watershed includes residential neighborhoods with aging infrastructure. Stormwater from streets, parking lots, and yards flows through the marsh system before reaching the ocean. After heavy rain, the USGS Makawao Stream gauge near Kailua can spike to 14x normal flow (recorded in April 2026), carrying sediment and bacteria toward Kailua Beach.
The City & County of Honolulu monitors bacteria levels at 7 stations along Kailua Bay through the Department of Environmental Services. This data, combined with DOH monitoring and USGS stream gauges, gives Kailua Beach some of the most comprehensive water quality coverage on Oʻahu.
The DOH website does not explain any of this context. They show a single data point — whether there is an advisory or not. This page combines city testing, stream discharge, and geographic analysis to give a more complete picture.
Less rainfall means less runoff through Kawainui Marsh. Stream flows are low. Water quality historically tests within baseline across the entire beach. Trade winds keep conditions pleasant.
Heavy rain drives elevated stream discharge. Brown water advisories are common. The south end of the beach is most affected. Kona storms can produce the worst conditions — windward Oʻahu receives the heaviest rainfall on the island.
Kailua receives approximately 50 inches of rain annually — more than Waikiki (20 in) but less than the Koʻolau summit (200+ in).
The Hawaii Department of Health recommends staying out of the ocean for at least 72 hours after heavy rain, even if the water looks clear. At Kailua Beach, this is important because the Kawainui Marsh system drains a large watershed into Kailua Bay. After storms, the south end of the beach near the stream outlets will be more affected than the north end toward Lanikai.
Free alerts when water quality changes at your beach — brown water advisories, bacteria warnings, and all-clear notices.
No spam. Just safety alerts for your trip.
100+ beaches and 25+ hotels across all 6 islands
Page last updated April 29, 2026. Live advisory data refreshes from the Hawaii DOH feed every 15 minutes.
⚠️ 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.
This site is a work in progress and we want to make it better. If you notice something that isn't working right, have a suggestion, or want to share local knowledge about a beach, please reach out.
This site does not recommend or advise anyone to swim at any beach. We share government data and geographic analysis so you can make your own informed decisions. By using this site you accept full responsibility for your own safety. See our Terms of Use for full details.
When in doubt, don't go out. 🤙