THE WEATHER BEAT · OCT 7

Flood Watch for Kauai, Niihau and Oahu from Wednesday evening into Thursday as southerly winds draw up tropical moisture

Kauai, Niihau and Oahu are under a Flood Watch from Wednesday evening through Thursday afternoon as a low north of the state draws up tropical moisture.

By the Weather Rock October 7, 2026, 8:05 a.m. · 5 min read

GOES satellite view of the event region — Kauai, Oahu and the islands to the east from GOES West at 5:30 p.m. HST Tuesday, 6 October 2026, before the Flood Watch was issued. Image: NOAA GOES-West GeoColor via NASA GIBS, 2026-10-07 03:30Z.

Key points

The Weather Service office in Honolulu issued a Flood Watch at 1:41 a.m. HST Wednesday for Kauai, Niihau and Oahu. It runs from Wednesday evening through Thursday afternoon.
A low pressure area forming far north of the islands is turning the winds southerly and pulling deep tropical moisture over the western half of the chain.
With the wind from the south, the rain may favor leeward areas such as the Waianae Coast and Honolulu, which flood more easily than the windward slopes.

Kauai and Oahu: a Flood Watch for Wednesday night into Thursday

On Tuesday evening the forecasters in Honolulu were not ready to issue a watch. Their 7:29 p.m. HST discussion said the computer guidance had "yet to produce a concise picture of a flood threat". It said they had "held off on issuing a Flood Watch until we see better model agreement."

Six hours later they issued one. The Flood Watch issued at 1:41 a.m. HST Wednesday covers all of Kauai, Niihau and Oahu, from Wednesday evening through Thursday afternoon. It says flash flooding caused by excessive rainfall is possible, and it warns that "training of heavy showers containing intense rain rates will be possible." Isolated thunderstorms are possible too.

The cause is far from the islands. A low was forming along a stalled front roughly 700 miles north of Kauai, near 30 north and 160 west by the Tuesday evening discussion. The usual trade winds have faded, and the flow is turning to come from the south. That southerly flow pulls tropical moisture up over the state. A jet stream to the east of the low adds lift aloft.

Direction matters here. Hawaii's rain usually falls on the windward, northeast-facing slopes. A south wind sends the showers onto the leeward side instead. The forecasters wrote that these areas "tend have a lower threshold for flooding." On Oahu that means the Waianae Coast, the Ewa Plain and Honolulu. On Kauai it means the south and west shores. The discussion said the heaviest rain was most likely late Wednesday night and early Thursday. It favored the western islands, though the rain could reach "as far east as Maui."

The low is expected to stall and weaken on Friday, and the discussion favored light trade winds returning on Monday.

Item	Detail (NWS Honolulu)
Product	Flood Watch, issued 1:41 a.m. HST Wed Oct 7
Where	Niihau; Kauai North, East, South, Southwest and Mountains; Waianae Coast and Mountains; Oahu North Shore; Central Oahu; Ewa Plain; Honolulu Metro; East Honolulu; Koolau Windward and Leeward; Olomana
When	Wednesday evening through Thursday afternoon (ends 6 p.m. HST Thursday)
What	Flash flooding caused by excessive rainfall is possible; training heavy showers, isolated thunderstorms
Impacts (product text)	Flood-prone roads and low-lying areas may be closed; urban areas may see more significant flooding from rapid runoff
Setup (AFD 7:29 p.m. HST Tue)	Low developing near 30N 160W; southerly flow; heaviest rain chance late Wed night to early Thu; low stalls and weakens Friday

*Sources: NWS Honolulu Flood Watch and Area Forecast Discussion, as issued. Times are Hawaii Standard Time.*

Elsewhere this morning

In eastern Iowa, the Wapsipinicon River near De Witt was still rising. NWS Quad Cities measured it at 12.1 feet at 7:30 p.m. CDT Tuesday, against a flood stage of 11.0 feet. It is forecast to crest at 12.7 feet early Thursday afternoon. The warning says "moderate flooding is occurring and major flooding is forecast." At 12.5 feet, the product says, water affects old U.S. Highway 61 near the river. The river is expected to fall below flood stage late Monday evening.

River	Stage (7:30 p.m. CDT Tue)	Flood stage	Forecast crest	Source
Wapsipinicon near De Witt 4S, IA	12.1 ft	11.0 ft	12.7 ft early Thu afternoon	NWS Quad Cities Flood Warning, 7:36 p.m. CDT Tue

This is a morning summary, not emergency information. For live warnings see weather.gov and your local officials. Hawaii: https://www.weather.gov/hfo/

The rock's live forecast for the places in this story