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TREND REPORT

Hawaii Water Quality — July 21, 2026

Oʻahu water quality is worsening (-57pp in 14 days)

By Safe to Swim Hawaii Team · Published July 21, 2026
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BIG ISLAND
Still advisory-free (100% advisory-free)
→
MAUI
Still advisory-free (100% advisory-free)
↓
OʻAHU
-57pp worsening
↓
KAUAʻI
-14pp worsening

Oʻahu ocean water quality worsened 57 percentage points over the last 14 days (100% advisory-free two weeks ago vs. 43% advisory-free now).

For a trip in the next week, prioritize islands with stronger structural protection (dry coasts, reef enclosure, no major streams). See cleanest Hawaiian island and BWA alternatives.

Where the islands stand today

Big Island

still advisory-free

Big Island has been persistently advisory-free — the same baseline as the prior two weeks. 0 of our 7 tracked beaches on the island have active advisory days in the last 30 days. NOAA's 7-day forecast is dry, so the persistently advisory-free baseline should hold. See the Big Island leaderboard for the beach-by-beach ranking.

Maui

still advisory-free

Maui has been persistently advisory-free — the same baseline as the prior two weeks. 0 of our 6 tracked beaches on the island have active advisory days in the last 30 days. NOAA's 7-day forecast is dry, so the persistently advisory-free baseline should hold. See the Maui leaderboard for the beach-by-beach ranking.

Oʻahu

worsening

Oʻahu is worsening over the last 14 days (-57pp vs. the prior two weeks). Our 12 tracked beaches happen not to overlap with the DOH advisories driving this signal — the worsening trend is from island-wide or other-area advisory events. NOAA's 7-day forecast is wet (peak 51% chance of rain) — expect the pattern to shift toward more advisories. See the Oʻahu leaderboard for the beach-by-beach ranking.

Kauaʻi

worsening

Kauaʻi is worsening over the last 14 days (-14pp vs. the prior two weeks). Our 6 tracked beaches happen not to overlap with the DOH advisories driving this signal — the worsening trend is from island-wide or other-area advisory events. NOAA's 7-day forecast is wet (peak 55% chance of rain) — expect the pattern to shift toward more advisories. See the Kauaʻi leaderboard for the beach-by-beach ranking.

Advisory-free leaders today (last 30 days)
Ala Moana Beach Park
30/30 days advisory-free
Advisory-free →
Anaehoʻomalu Bay (A-Bay)
30/30 days advisory-free
Advisory-free →
Anini Beach
30/30 days advisory-free
Advisory-free →
Most advisoried beaches today (last 30 days)
Waimea Bay
30/30 days advisory-free
Under advisory →
Wailea Beach
30/30 days advisory-free
Under advisory →
Turtle Bay Beach
30/30 days advisory-free
Under advisory →
NOAA 7-day forecast, per island tourist coast
  • Kohala Coast, Big Island: dry (max 14% chance of rain across next 7 days)
  • South Maui (Wailea / Kihei): dry (max 17% chance of rain across next 7 days)
  • South Shore O’ahu (Honolulu / Waikiki): wet (max 51% chance of rain across next 7 days)
  • Po’ipu, Kaua’i: wet (max 55% 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
Hub →
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: Statistics in this report come from our pipeline's aggregation of Hawaii DOH Clean Water Branch advisory data across 31 tracked beaches (last 14 days compared against the 14 days before). Forecast data from NOAA National Weather Service (api.weather.gov) sampled at each island's primary tourist coast. All numbers accurate as of publication. This report describes water-quality trends and forecast; it is not a swim recommendation. Physical hazards (shore break, rip currents, surf, marine life) are independent of water quality. Always check the individual beach page and local conditions before entering the water.