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TREND REPORT

Hawaii Water Quality — September 21, 2026

Maui share of days with no DOH advisory anywhere on the island fell 43pp between 14-day windows

By Safe to Swim Hawaii Team · Published September 21, 2026
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BIG ISLAND
Mostly advisory-affected, stable (0% of days without an island advisory)
↓
MAUI
-43pp worsening (36% of days without an island advisory)
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OʻAHU
Mostly advisory-affected, stable (0% of days without an island advisory)
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KAUAʻI
Mostly advisory-affected, stable (0% of days without an island advisory)

The share of days with no DOH advisory anywhere on Maui fell 43 percentage points (79% in the prior 14-day window vs. 36% in the latest 14-day window).

This is a posted-advisory history metric, not a direct bacteria test or swimming-safety finding. Check the Maui leaderboard, the individual beach page, and live DOH status for current context.

Where the islands stand today

Big Island

mostly advisory-affected

Big Island has remained mostly advisory-affected across both 14-day island-wide advisory-day windows (0% of days had no DOH advisory anywhere on the island in the latest window). All 7 of our tracked beaches on the island recorded one or more advisory days in that 30-day history window. NOAA's 7-day rainfall signal is mild. Rainfall probability does not predict whether DOH will issue or lift an advisory. See the Big Island leaderboard for the beach-by-beach ranking.

Maui

worsening

Maui is worsening over the last 14 days (-43pp vs. the prior two weeks). All 6 of our tracked beaches on the island recorded one or more advisory days in that 30-day history window. NOAA's 7-day rainfall signal is mild. Rainfall probability does not predict whether DOH will issue or lift an advisory. See the Maui leaderboard for the beach-by-beach ranking.

Oʻahu

mostly advisory-affected

Oʻahu has remained mostly advisory-affected across both 14-day island-wide advisory-day windows (0% of days had no DOH advisory anywhere on the island in the latest window). All 12 of our tracked beaches on the island recorded one or more advisory days in that 30-day history window. NOAA's 7-day rainfall signal is mild. Rainfall probability does not predict whether DOH will issue or lift an advisory. See the Oʻahu leaderboard for the beach-by-beach ranking.

Kauaʻi

mostly advisory-affected

Kauaʻi has remained mostly advisory-affected across both 14-day island-wide advisory-day windows (0% of days had no DOH advisory anywhere on the island in the latest window). All 6 of our tracked beaches on the island recorded one or more advisory days in that 30-day history window. NOAA's 7-day rainfall signal is mild. Rainfall probability does not predict whether DOH will issue or lift an advisory. See the Kauaʻi leaderboard for the beach-by-beach ranking.

Historical advisory-free leaders (last 30 days)

These counts describe the recorded history. Check each beach's current status for active DOH advisories.

Hoʻokipa Beach Park
27/30 days advisory-free
Check current status →
Kaʻanapali Beach
27/30 days advisory-free
Check current status →
Makena Beach
27/30 days advisory-free
Check current status →
Most advisory-affected tracked beaches (last 30 days)
Honoliʻi Beach
0/30 days advisory-free
30 advisory days →
Sunset Beach
9/30 days advisory-free
21 advisory days →
Haleiwa Beach Park
12/30 days advisory-free
18 advisory days →
NOAA 7-day forecast, per island tourist coast
  • Kohala Coast, Big Island: mild (peak 42%, average 22% chance of rain across the forecast periods)
  • South Maui (Wailea / Kihei): mild (peak 33%, average 12% chance of rain across the forecast periods)
  • South Shore O’ahu (Honolulu / Waikiki): mild (peak 38%, average 19% chance of rain across the forecast periods)
  • Po’ipu, Kaua’i: mild (peak 31%, average 21% chance of rain across the forecast periods)

For the always-live per-island outlook, see our Hawaii Water Quality Forecast, which regenerates daily from NOAA + DOH data.

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Live data and deeper context
Hawai’i Water Quality Data Hub — every resource in one place
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Hawaii Water Quality Forecast — 14-day trend + 7-day NOAA outlook
Live →
Is Hawaii’s Beach Water Getting Cleaner or Dirtier? — YoY DOH data
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Cleanest Hawaii Beaches Right Now — statewide ranking
Rankings →
Hawaii Citizen Water Testing — 100+ Surfrider BWTF sites
Coverage →
Why Hawaii Water Turns Brown After Rain — stream-mouth data
Data →
Hawaii Sewage Spills Today — live DOH tracker
Live →
Where to Swim During a Brown Water Advisory
Guide →
Brown Water Advisory — live all islands + 72-hour rule
Guide →
Previous report — September 20, 2026
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Methodology: The island trend uses Hawaii DOH island-wide advisory-day history where available: a day counts as advisory-free only when no DOH advisory was recorded anywhere on that island. If island history is unavailable, the generator labels its tracked-beach-fraction fallback explicitly. The separate beach list summarizes 31 tracked beach histories. Forecast data comes from NOAA National Weather Service (api.weather.gov) at each island's primary tourist coast. This report is not a swim recommendation; always check the individual beach page and current local conditions before entering the water.