West Kaua’i

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Lows 70 to 81 near the shore to around 62 above 3000 feet. East winds 10 to 15 mph.

Sunday: Mostly sunny. Highs 86 to 92 near the shore to around 78 above 3000 feet. East winds up to 15 mph.

Sunday Night: Partly cloudy. Lows 70 to 81 near the shore to around 62 above 3000 feet. East winds 10 to 15 mph.

South Kaua’i

Tonight: Mostly cloudy with scattered showers. Lows 72 to 80. Northeast winds 10 to 15 mph. Chance of rain 40 percent.

Sunday: Partly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 80 to 90. Northeast winds around 15 mph. Chance of rain 40 percent.

Sunday Night: Mostly cloudy with isolated showers. Lows 72 to 79. Northeast winds around 15 mph. Chance of rain 20 percent.

Kaua’i Mountains

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 62 to 68 in the valleys to around 59 above 4000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Sunday: Partly sunny with scattered showers. Highs 76 to 83 in the valleys to around 69 above 4000 feet. East winds around 15 mph. Chance of rain 50 percent.

Sunday Night: Mostly cloudy with scattered showers. Lows 61 to 67 in the valleys to around 59 above 4000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

North Kaua’i

Tonight: Mostly cloudy with scattered showers. Lows 60 to 74. East winds 10 to 15 mph. Chance of rain 40 percent.

Sunday: Partly sunny with scattered showers. Highs 73 to 88. East winds 10 to 15 mph. Chance of rain 50 percent.

Sunday Night: Mostly cloudy with isolated showers. Lows 60 to 74. East winds 10 to 15 mph. Chance of rain 20 percent.

East Kaua’i

Tonight: Mostly cloudy with scattered showers. Lows 66 to 77. East winds 10 to 15 mph. Chance of rain 50 percent.

Sunday: Mostly cloudy with scattered showers. Highs 79 to 86. East winds around 15 mph. Chance of rain 50 percent.

Sunday Night: Mostly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows 66 to 77. Northeast winds 10 to 15 mph. Chance of rain 40 percent.

Detailed Forecast

Synopsis

Moderate to locally breezy trade winds will continue through Monday before gradually decreasing by midweek. Another round of moisture will move in from the east by next Tuesday, increasing shower activity across the state.

Short term update

No major updates were made this evening as the previous forecast remains on track.

Prev discussion

Issued at 317 PM HST Sat Sep 19 2026 Have nudged the forecast to the latest National Blend of Models, but the forecast philosophy hasn't changed much. The GFS and ECMWF global models are coming into better agreement with regards to the upper level trough placement and strength near the western islands early next week. There is general agreement that the trough will linger just west of Kauai for another day, and then slowly moves the trough to the east, and then lifts it northward, with the trough lingering near the islands. Meanwhile, the remnants of former Tropical Depression 15E remain to the southeast of the islands. As that system moves to the west, a trough associated with it will bring moisture towards the islands, which will increase shower activity midweek. That trough will also help to disrupt the trade wind flow.
The above mentioned upper level trough is helping to draw high clouds northward over the islands. Meanwhile the trade wind flow is focusing lower clouds and showers to the more typical windward and mauka areas. Heading into Monday night, the trough mentioned above that will begin to disrupt the trade wind flow over the islands resulting in a weakening in the trades. Dewpoints are expected to remain in the lower 70s, so expect muggy conditions to continue, and as the winds weaken, it will feel even muggier.
The global models had delayed the arrival of the unstable air with the trough a bit compared to 24 hours ago. Its now looking like the most unstable airmass associated with the trough won't move into the Big Island until early Wednesday. With precipitable water vales once again reaching over 2″, heavier showers are likely. With timing and placement still being flushed out in the models, have held off putting any details in the forecast.
The long term forecast will also be dependent on how models handle the remnants of Tropical Depression 15-E. Environmental conditions are conducive for some development next week according to the NHC. Given the chance for this forecast to change, please continue to monitor the status of tropical cyclone development through nhc.noaa.gov, and local weather forecasts at weather.gov/hfo.

Aviation

Issued at 317 PM HST Sat Sep 19 2026 Breezy trades will persist through the weekend and continue to focus clouds and isolated to scattered showers over windward and mountain areas. In addition to the windward shower activity, isolated to scattered showers have developed over the Kona slopes of the Big Island this afternoon and are expected to develop again tomorrow, though coverage may be less due to slightly drier conditions.
AIRMET Tango remains in effect for moderate low-level turbulence downwind of island terrain due to the breezy trade winds. This AIRMET will likely be needed through much of the weekend.

Marine

Issued at 317 PM HST Sat Sep 19 2026 A weak axis of high pressure is anchored along 35N while surface pressure falls remain prominent S/SE of the islands. The resulting gradient maintains locally strong trades through at least the first half of next week. The Small Craft Advisory for the typical windy waters around Maui County and Big Island is now in effect through Monday afternoon. A weak tropical disturbance potentially brings strengthening trades, a greater coverage showers, and isolated thunderstorms, during the middle of next week.
Surf along S shores remains above average through the weekend as long period SSW swell holds steady. This swell then fades during the middle of the week only to be followed by a small S swell shortly thereafter.
Trades maintain moderate surf along E shores well into next week. Surf along N shores remains flat to tiny with a minor bump possible Tuesday into Wednesday of next week. A small long period WNW swell then builds late next week.

Fire weather

Issued at 317 PM HST Sat Sep 19 2026 Fire weather risk remains low due to residual moisture across the state. Moderate to locally breezy trade winds are expected through Monday, and should filter in some relatively drier air for that time period. Inversion heights are around 6000 feet.

HFO Watches/Warnings/Advisories

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

Kauai Now Weather is brought to you by Blue Hawaiian Helicopters.

Check out their Kaua‘i Helicopter Tours today!

Data Courtesy of NOAA.gov