Hawaii Will Face Increased Rain and Flash Flooding

The state expects a weather shift bringing heavier rainfall and flash flooding potential beginning next Wednesday.

Updated on Oct. 4, 2026 in Forecasts

Heavy rain falls over a lush, steep volcanic ridgeline in Hawaii beneath a thick layer of grey storm clouds. — Hawaii will experience a transition toward increased rain and flash flooding potential beginning October 7, 2026, as a trough pulls tropical moisture over the islands. AI Illustration. Upload story photo >

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Is your household prepared for the potential flooding and heavy rain forecast for next week?

Hawaii will experience a transition toward increased rain and flash flooding potential beginning October 7, 2026. This shift follows a period of stable conditions and moderate trade winds that are expected to last through early next week.

Why it matters

A trough moving into the region from the northwest will pull tropical moisture over the islands. This shift will create conditions favorable for heavier rain and potential flash flooding on Kauai and Oahu by the middle of the week.

A small craft advisory remains in effect for coastal and channel waters around Maui County and Hawaii Island until 6 p.m. on October 4, 2026. A small long-period swell is also expected to arrive late Sunday for south-facing shorelines.

The details

The upcoming weather pattern is driven by an early-season trough that will settle northwest of the islands. This system will pull tropical moisture northward, leading to lighter winds by Tuesday and subsequent afternoon cloud cover and showers.

October 4, 2026: Small craft advisory ends at 6 p.m.
October 4, 2026: Monthly box jellyfish influx begins on Oahu.
October 6, 2026: Expected transition to lighter winds.
October 7, 2026: Potential for heavier rain and flash flooding begins.

Forecasts
Oct. 7
Hawaii Flood Watch Issued for Kauai and Oahu
Forecasts
Sept. 23
Hawaii Declared Emergency Ahead of Tropical Storm
Surfing
Sept. 25
Hawaii County Issued High Surf Advisories

Seasonal Patterns

This weather event follows established meteorological patterns monitored by the National Weather Service's Flash Flood Warning criteria. It reflects common seasonal transitions as early-season troughs interact with tropical moisture to increase local flood risks.

Residents should remain aware of potential flash flooding on Kauai and Oahu beginning Wednesday night. Those near south and west-facing shores on Oahu should prepare for the monthly box jellyfish influx starting Sunday.

The takeaway

Monitoring official weather updates is essential as the islands transition toward wetter conditions next week. Residents should prioritize safety by avoiding low-lying areas prone to flooding during heavy rainfall events.