West Kaua’i

Tonight: Mostly cloudy with scattered showers. Lows around 67 near the shore to around 57 above 3000 feet. Northeast winds up to 10 mph. Chance of rain 50 percent.

Monday: Partly sunny with scattered showers. Highs around 81 near the shore to around 69 above 3000 feet. Southeast winds up to 10 mph. Chance of rain 50 percent.

Monday Night: Partly cloudy. Scattered showers early in the evening, then isolated showers in the late evening and overnight. Lows around 66 near the shore to around 56 above 3000 feet. Light winds. Chance of rain 40 percent.

South Kaua’i

Tonight: Mostly cloudy with numerous showers. Lows around 67. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

Monday: Mostly cloudy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 76 to 82. East winds around 10 mph. Chance of rain 70 percent.

Monday Night: Mostly cloudy with scattered showers until early morning, then partly cloudy with isolated showers early in the morning. Lows around 66. Light winds. Chance of rain 50 percent.

Kaua’i Mountains

Tonight: Mostly cloudy with occasional showers. Lows 59 to 66 in the valleys to around 55 above 4000 feet. East winds up to 10 mph in the evening becoming light. Chance of rain 90 percent.

Monday: Mostly cloudy. Occasional showers early in the morning, then numerous showers late in the morning. Scattered showers in the afternoon. Highs 72 to 78 in the valleys to around 62 above 4000 feet. Light winds becoming southeast up to 10 mph in the afternoon. Chance of rain 90 percent.

Monday Night: Mostly cloudy until early morning then becoming partly cloudy. Scattered showers in the evening, then isolated showers after midnight. Lows 58 to 65 in the valleys to around 54 above 4000 feet. Southeast winds up to 10 mph shifting to the southwest after midnight. Chance of rain 50 percent.

North Kaua’i

Tonight: Mostly cloudy with numerous showers. Lows 60 to 69. Southeast winds up to 10 mph. Chance of rain 70 percent.

Monday: Mostly cloudy. Numerous showers early in the morning, then scattered showers in the late morning and afternoon. Highs 72 to 81. Southeast winds up to 15 mph. Chance of rain 70 percent.

Monday Night: Partly cloudy. Scattered showers early in the evening, then isolated showers in the late evening and overnight. Lows 60 to 67. Light winds. Chance of rain 40 percent.

East Kaua’i

Tonight: Mostly cloudy with numerous showers. Lows 61 to 71. East winds up to 15 mph. Chance of rain 70 percent.

Monday: Mostly cloudy. Numerous showers early in the morning, then scattered showers in the late morning and afternoon. Highs 69 to 81. East winds up to 15 mph. Chance of rain 70 percent.

Monday Night: Mostly cloudy with scattered showers until early morning, then partly cloudy with isolated showers early in the morning. Lows 60 to 70. Light winds. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Mostly dry and pleasant trade wind weather will continue into Monday, with brief passing showers favoring windward and mauka areas. A significant pattern change is expected by Tuesday as an upper disturbance and surface low pressure evolve northwest of the islands. This system is forecast to draw deep tropical moisture northward over the state, leading to an extended period of southerly winds, increased chances for widespread rainfall, and renewed flooding concerns from the middle of the week through the weekend.

Short term update

Issued at 836 PM HST Sun Apr 5 2026 A diffuse band of scattered showers caught up in the trades lies over and to the east of Oahu this evening. As the trades continue to veer and weaken, HREF and REFS both show this band slowly beginning to pull west-northwestward and slowly expanding overnight, eventually including mainly windward and mauka sections of Kauai as well. With little upper support, these showers will not amount to too much.
A digging shortwave trough east of Midway tonight will push rapidly ESE down the Northwest Hawaiian Islands through Monday. The high resolution ensembles show the trough aloft should be close enough to begin locally enhancing showers over and near Kauai Monday night in the SE flow. A few of these might become briefly heavy as this leading shortwave gets close and mid-level temperatures cool for a while, but instability will still be limited at this point.

Prev discussion

Issued at 417 PM HST Sun Apr 4 2026 This afternoon, relatively quiet weather continues across the islands with only a few light showers embedded within moderate trade winds noted in regional satellite and radar imagery. In addition, the typical dayThe latest high resolution guidance shows that atime increase in cloud cover has occurred over the Kona slopes of the Big Island, though little to no shower activity has been observed there today. Moderate easterly trade winds will continue to focus mainly light showers along windward and mauka slopes, while leeward areas remain mostly dry through Monday.
By Monday night, trade wind flow will be disrupted as the surface ridge to the north erodes and a broad surface trough develops northwest of the islands. As a result, weaker background surface winds will begin to veer out of the southeast to south from Tuesday through Wednesday. Guidance indicates that this also will mark the beginning of a series of shortwave troughs that are expected to dig southeastward towards the main Hawaiian Islands in what will be a notable amplification and shift in the large scale pattern across the Central Pacific for the rest of this week. As background flow becomes more southerly, models remain in good agreement that deep tropical moisture will be drawn northward once again over the islands as early as Tuesday but especially by Wednesday. This increasing moisture combined with daytime heating, sea breezes, and a potent shortwave trough moving through may even trigger some heavy showers over interior areas on Tuesday afternoon.
From Wednesday through the end of the week, potential for more widespread rainfall and flooding will return. Upper-level forcing is expected to strengthen as a strong shortwave rounds the base of the trough, potentially enhancing lift over the region while low pressure organizes west of the islands. The combination of deep moisture, increasing large-scale forcing for ascent, and southerly winds (which could be gusty at times) all point towards yet another widespread and organized rainfall event for the state. In addition to the rainfall concerns during this period, some strong to severe thunderstorms along with gusty downsloping winds for north and windward sides of the islands can't be ruled out.
There remain some differences among global models by next weekend, but the general consensus is that the active pattern could linger, with the potential for rain across at least portions of the state persisting through the weekend and beyond where the deep moisture axis anchors.
As previous discussion have mentioned, one important consideration with this week's rainfall is antecedent conditions. The islands experienced significant flash flood events in recent weeks, and despite several days of drier trade wind weather, soils remain vulnerable in many areas. As a result, any period of high rainfall rates could quickly lead to enhanced runoff, renewed rises in streams and reservoirs, and localized flash flooding concerns.
Some tweaks have been made with this afternoon's forecast updates, primarily for QPF and timing. This system will continue to be monitored closely over the coming days, and additional adjustments to timing, duration, and impact messaging are possible as details become more clear.

Aviation

Issued at 417 PM HST Sun Apr 4 2026 Mild to locally breezy trades will continue to prevail through the period. Periodic shower activity along windward sites may briefly bring conditions down to MVFR, however widespread VFR conditions are generally expected. Winds are expected to shift more east and even southeast during the day tomorrow across the islands.
No AIRMETS are in effect and none are expected through the next 24 hours.

Marine

Issued at 417 PM HST Sun Apr 4 2026 Moderate to locally fresh trades will persist for the next day or so as high pressure north of the islands moves slowly eastward. Winds will ease and shift southeasterly Monday night through Wednesday as a front stalls out and merges with a trough just west of the islands. The winds will turn more southerly and increase to moderate and strong levels on Thursday as a storm system develops along the trough west of the state.
Small northwest swells will keep some small surf along north facing shores through Monday. A moderate long-period northwest swell will fill in Monday night and Tuesday, giving more of a boost to north shore surf late Tuesday through Wednesday.
A small southerly swell will keep some small surf in place along south facing shores through Monday. A slightly larger, long-period south swell, will fill in Monday night. This swell will give a more noticeable increase to south shore surf Tuesday into next weekend. Strengthening southerly winds could make for choppy seas by late next week.
East shore surf will remain small and below the seasonal average during the next 7 days due to a lack of strong trade winds over and upstream of the islands.

HFO Watches/Warnings/Advisories

None.

Data Courtesy of NOAA.gov