West Kaua’i

Tonight: Partly cloudy. Breezy. Lows around 75 near the shore to around 66 above 3000 feet. Northeast winds up to 20 mph.

Monday: Sunny and breezy. Highs 86 to 92 near the shore to around 79 above 3000 feet. Northeast winds up to 20 mph.

Monday Night: Mostly clear. Lows around 75 near the shore to around 65 above 3000 feet. Northeast winds up to 15 mph.

South Kaua’i

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Breezy. Isolated showers. Lows 72 to 78. Northeast winds 15 to 25 mph. Chance of rain 20 percent.

Monday: Mostly sunny. Breezy. Isolated showers in the morning. Highs 80 to 90. Northeast winds 15 to 25 mph. Chance of rain 20 percent.

Monday Night: Partly cloudy. Isolated showers after midnight. Lows 71 to 78. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Kaua’i Mountains

Tonight: Breezy. Mostly cloudy with scattered showers. Lows around 71 in the valleys to around 63 above 4000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Monday: Breezy. Mostly sunny with scattered showers. Highs 76 to 84 in the valleys to around 74 above 4000 feet. East winds 10 to 20 mph. Chance of rain 40 percent.

Monday Night: Partly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows around 70 in the valleys to around 62 above 4000 feet. East winds 10 to 15 mph. Chance of rain 40 percent.

North Kaua’i

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Scattered showers. Lows 66 to 77. East winds up to 15 mph. Chance of rain 30 percent.

Monday: Mostly sunny with isolated showers. Highs 73 to 88. East winds up to 15 mph. Chance of rain 20 percent.

Monday Night: Partly cloudy. Isolated showers after midnight. Lows 66 to 76. East winds 10 to 15 mph. Chance of rain 20 percent.

East Kaua’i

Tonight: Mostly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows 68 to 78. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Monday: Mostly sunny with isolated showers. Highs 79 to 87. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Monday Night: Mostly cloudy with isolated showers. Lows 67 to 77. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Breezy trades weaken slightly during midweek then restrengthen by late in the week. Potential tropical development threatens to bring heavy rainfall to eastern portions of the state during the latter half of the week, though uncertainty remains higher than usual at this time.

Short term update

Moderately stable breezy trades prevail at press with limited showers observed on area radar composite. SW flow around the periphery of a trough positioned northwest of the islands is drawing high clouds northward over area skies, but it is not a particularly meaningful feature otherwise. Dry mid-level air encroaching from the NE will further strengthen stability over the western half of the state on Monday while deeper moisture entrained in the trades reaches the Big Island resulting in a greater coverage of windward showers there.

Aviation

Issued at 312 PM HST Sun Sep 20 2026 Breezy trades will continue into Monday. Isolated showers and brief MVFR conditions are possible mainly over windward and mountain areas. Shower activity may increase by Monday night, especially over windward areas of Big Island.
AIRMET Tango remains in effect for moderate low-level turbulence downwind of island terrain due to the breezy trades.

Marine

Issued at 312 PM HST Sun Sep 20 2026 The gradient between weak high pressure north of the islands and pressure falls south of the islands will maintain fresh to locally strong trade winds across the region through at least Monday night. Therefore, the Small Craft Advisory has been extended through Monday night for the typical windy channels and waters of Maui County and the Big Island. After a slight reduction in trade wind speeds heading into mid week, they will restrengthen during the latter half of the week as a trough or potential weak tropical disturbance moves south of the islands. Shower coverage will also increase, along with the potential for isolated thunderstorms, particularly across the eastern waters.
Surf along south facing shores will remain above average over the next couple of days as a long period SSW swell holds relatively steady. This swell will then gradually fade heading into mid week. A slightly smaller, long-period south-southwesterly swell will fill in late this week into next weekend generated by a series of lows near New Zealand. West facing shores will experience a bit of the southerly wrap through most of the week.
Breezy trade winds will maintain moderate surf along east facing shores for the next several days. Surf along north facing shores will remain flat to tiny through Monday, but will see a slight bump Tuesday into Wednesday as a small, medium-period northwest swell fills in from an Aleutian low. Then a small, long-period west-northwest swell expected to be generated by Tropical Storm Dujuan as it curves northeast near Japan and potentially strengthens into a hurricane will build locally Friday into next weekend, increasing surf along north and west facing shores.

Fire weather

Issued at 312 PM HST Sun Sep 20 2026 Fire weather risk remains low. Locally breezy trade winds are expected through at least Monday. However, dewpoints in the low 70s will keep relative humidity in check. Inversion heights are around 6000 feet statewide.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 AM HST Tuesday for Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters, Maalaea Bay, Pailolo Channel.

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Data Courtesy of NOAA.gov