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TREND REPORT

Hawaii Water Quality — August 18, 2026

Big Island share of days without any island-wide DOH advisory fell 50pp between 14-day windows

By Safe to Swim Hawaii Team · Published August 18, 2026
↓
BIG ISLAND
-50pp worsening (50% of days without an island advisory)
↑
MAUI
+14pp improving (79% of days without an island advisory)
↑
OʻAHU
+14pp improving (14% of days without an island advisory)
→
KAUAʻI
Mostly advisory-affected, stable (0% of days without an island advisory)

The share of days with no DOH advisory anywhere on Big Island fell 50 percentage points (100% in the prior 14-day window vs. 50% in the latest 14-day window).

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

Where the islands stand today

Big Island

worsening

Big Island is worsening over the last 14 days (-50pp vs. the prior two weeks). 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 forecast is mild — scattered showers possible but unlikely to drive new advisories. See the Big Island leaderboard for the beach-by-beach ranking.

Maui

improving

Maui is improving over the last 14 days (+14pp vs. the prior two weeks). 6 of our 6 tracked beaches on the island recorded one or more advisory days in that 30-day history window. NOAA's 7-day forecast is mild — scattered showers possible but unlikely to drive new advisories. See the Maui leaderboard for the beach-by-beach ranking.

Oʻahu

improving

Oʻahu is improving over the last 14 days (+14pp vs. the prior two weeks). 12 of our 12 tracked beaches on the island recorded one or more advisory days in that 30-day history window. NOAA's 7-day forecast is wet (peak 52% chance of rain) — expect the pattern to shift toward more advisories. 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 forecast is mild — scattered showers possible but unlikely to drive new advisories. See the Kauaʻi leaderboard for the beach-by-beach ranking.

Advisory-free leaders today (last 30 days)
Ala Moana Beach Park
28/30 days advisory-free
Advisory-free →
Anini Beach
28/30 days advisory-free
Advisory-free →
Banzai Pipeline
28/30 days advisory-free
Advisory-free →
Most advisory-affected tracked beaches (last 30 days)
Haleiwa Beach Park
2/30 days advisory-free
28 advisory days →
Hanakaʻoʻo Beach Park
22/30 days advisory-free
8 advisory days →
Sunset Beach
26/30 days advisory-free
4 advisory days →
NOAA 7-day forecast, per island tourist coast
  • Kohala Coast, Big Island: mild (max 42% chance of rain across next 7 days)
  • South Maui (Wailea / Kihei): mild (max 28% chance of rain across next 7 days)
  • South Shore O’ahu (Honolulu / Waikiki): wet (max 52% chance of rain across next 7 days)
  • Po’ipu, Kaua’i: mild (max 46% chance of rain across next 7 days)

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
Trend →
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 — April 23, 2026
Archive →
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.