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Flood Watch Issued for Parts of Hawaii

September 18, 2026 · wweather1 editorial · 1 min read

The National Weather Service in Honolulu has issued a Flood Watch for multiple islands due to remnant moisture from former Tropical Storm Norbert. The watch remains in effect through the early morning hours of September 18.

A Flood Watch has been issued by NWS Honolulu HI starting on September 17 at 5:40 PM HST and extending until September 18 at 6:00 AM HST. The affected areas include Maui, Lanai, Molokai, The Big Island, and Kahoolawe.

Remnant moisture from former Tropical Storm Norbert is bringing periods of moderate to heavy showers, primarily to the windward sides of the Hawaiian Islands through late tonight. Additionally, a band of moisture will move west across the islands through Friday, bringing isolated thunderstorms that could produce briefly higher rain rates and increase the risk of flash flooding.

Potential impacts include elevated runoff and overflowing streams, which may cause flood-prone roads and other low-lying areas to close. Urban areas may also experience more significant flooding and property damage due to rapid runoff.

Why it is dangerous and what to do

⚠️ Safety
• Monitor later forecasts from the National Weather Service.
• Be prepared to take action should Flash Flood Warnings be issued.
📊 The numbers, from wweather1 data
Hilo: now +26°, Overcast.
The record for this date is +29° (2025).
Three-day forecast: 13 October: +26°/+21° · 14 October: +27°/+20° · 15 October: +27°/+19°
The figures are computed automatically from the Open-Meteo/ERA5 archive — no eyeball estimates.
📰 Data source: NWS. Forecast and analysis — wweather1, based on Open-Meteo / met.no data.

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