Deep Tropical Moisture to Bring Heavy Rain, Flood Risk Across Hawaii

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A developing low pressure system northwest of the Hawaiian islands is tapping into deep tropical moisture, resulting in a more humid, unsettled weather pattern across the state. This will bring increasing showers, thunderstorms, and a growing threat of flash flooding from midweek into the weekend.

Why it matters

Hawaii is prone to heavy rain and flooding events, which can lead to property damage, transportation disruptions, and safety risks for residents. This developing storm system has the potential to bring widespread heavy rainfall that could overwhelm already saturated soils and trigger runoff, fast-rising streams, and localized flooding.

The details

Forecast guidance shows greater instability over Kauai and the Big Island, where afternoon showers may become more frequent and locally heavy. Winds will also trend southerly, pulling additional moisture north from the tropics and boosting rain chances across the state. Conditions are expected to become more active Tuesday night into Wednesday as moisture continues to deepen and another disturbance increases lifting in the atmosphere. A flood watch is in effect from Wednesday morning through Friday afternoon for all islands, and a Winter Storm Watch is posted for the Big Island summits above 12,500 feet for possible snow and freezing rain.

• A flood watch is in effect from Wednesday morning through Friday afternoon for all islands.
• A Winter Storm Watch is posted for the Big Island summits above 12,500 feet through Friday.

What they’re saying

What’s next

The wet pattern is expected to persist into the weekend, and any meaningful improvement may hold off until the middle of next week. Residents should stay alert for changing conditions, especially during heavier downpours, and heed any flood watches or warnings issued by local authorities.