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FORECAST WATCH

Hawaii Water Quality — September 16, 2026

Wet forecast for Oʻahu, Kauaʻi — check current beach advisories

By Safe to Swim Hawaii Team · Published September 16, 2026
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BIG ISLAND
Mostly advisory-affected, stable (0% of days without an island advisory)
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MAUI
Steady (43% 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)

NOAA's 7-day forecast shows wet weather for Oʻahu, Kauaʻi. Rain can increase runoff risk, but rainfall probability does not predict whether or when DOH will issue an advisory. If you have a beach day scheduled this week, check the live forecast page and the BWA alternatives guide.

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

stable

Maui is stable — no significant change in the last 14 days. 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 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 wet (peak 63% chance of rain). Rain can increase runoff risk; check current DOH advisories and local conditions. 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 wet (peak 61% chance of rain). Rain can increase runoff risk; check current DOH advisories and local conditions. 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
22/30 days advisory-free
Check current status →
Kaʻanapali Beach
22/30 days advisory-free
Check current status →
Keawakapu Beach
22/30 days advisory-free
Check current status →
Most advisory-affected tracked beaches (last 30 days)
Sunset Beach
5/30 days advisory-free
25 advisory days →
Waimea Bay
12/30 days advisory-free
18 advisory days →
Turtle Bay Beach
12/30 days advisory-free
18 advisory days →
NOAA 7-day forecast, per island tourist coast
  • Kohala Coast, Big Island: mild (peak 58%, average 20% chance of rain across the forecast periods)
  • South Maui (Wailea / Kihei): mild (peak 59%, average 17% chance of rain across the forecast periods)
  • South Shore O’ahu (Honolulu / Waikiki): wet (peak 63%, average 38% chance of rain across the forecast periods)
  • Po’ipu, Kaua’i: wet (peak 61%, average 42% 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
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
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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 14, 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.