Trip planners this week face two Hawaiis. Maui and the Big Island are running fully clean. Oʻahu and Kauaʻi are still recovering from the April 10 Kona Low. NOAA forecasts dry for most of the state — recovery should start within days.
Two weeks ago, Maui had only 43% of beach-days advisory-free. Today it is at 100% — the biggest 14-day improvement of any Hawaiian island in our tracking. Two weeks ago, Oʻahu had 32% of beach-days clean; today it is at 0%. Kauaʻi went from 57% clean to 0% clean. The Big Island held steady near 100% throughout. This is the sharpest divide weʻve seen this season between the leeward-dry coasts and the storm-exposed wetter ones.
The April 10 Kona Low hit all four islands with heavy rain. Two weeks later, you can trace every island’s current water-quality status back to its geography — not to whether the storm was bad, but to whether the coast can shed rain quickly.
The Big Island’s Kohala Coast gets under 10 inches of rain per year. No meaningful streams reach the resort beaches. The Kona Low barely registered in the monitoring data there. It’s still near 100% clean across our tracked sample.
South Maui sits in Haleakala’s rain shadow. Wailea gets ~12 inches of rain per year. The Kona Low pushed Maui below 50% for a week, but Wailea, Makena, and Keawakapu recovered fastest — and as of this week, every tracked Maui beach is back to advisory-free.
Oʻahu has the Ala Wai Canal + a dense cesspool belt on the Windward side. When rain hits upland, runoff reaches the South Shore through the canal and the Windward beaches through stream discharge. Recovery takes 7-14 days even after the rain stops — and the island-wide Brown Water Advisory DOH issued April 10 is still in effect on many beaches.
Kauaʻi has the steepest rainfall gradient in the state. Mount Waiʻaleʻale averages 450+ inches/year. The Kona Low pushed the North Shore rivers into prolonged discharge. Hanalei Bay, Anini, and the Na Pali coast beaches have been under advisory for most of the last 14 days. The South Shore (Poʻipu, Brennecke) cleared faster but was still pulled into the island-wide BWA count.
NOAA’s 7-day forecast at each island’s tourist coast as of publication:
For a live, always-current version of this analysis, see our new Hawaii Water Quality Forecast page, which regenerates daily and combines the 14-day trend with the latest NOAA outlook for each island.
Prioritize Big Island (Kohala Coast) or South Maui (Wailea-Makena). Both are fully clean, both have dry weather forecast, both are structurally low-advisory coasts. If youʻre locked into Oʻahu, Ko Olina is the strongest pick — the lagoons are sheltered from island-wide BWAs by their rock breakwaters. For Kauaʻi, Poʻipu on the south shore will clear fastest.
If the dry-week forecast holds, Oʻahu should be substantially recovered by May 1-3. Kauaʻi North Shore (Hanalei, Anini, Tunnels) will take longer — possibly into the second week of May depending on whether any new storms hit. Maui and Big Island should remain clean.
If water quality is a deciding factor and you havenʻt booked yet, our family trip planning guide has the four historically-cleanest resort areas with the data behind them. For general first-timer advice, see which Hawaiian island to visit first. Or, for the straight live numbers: cleanest Hawaii beaches right now and cleanest Hawaiian island.
Based on the current forecast + the typical Kona Low recovery curve, we expect Oʻahuʻs 14-day trend to cross from “worsening” to “improving” by the end of next week, and Kauaʻi South Shore to be substantially cleaner. North Shore Kauaʻi will lag. Maui and Big Island should remain fully clean. If a new Kona Low forms before April 30 (no sign of one in current forecasts), all bets are off.