Tropical air mass brings heavy showers and flood risk through midweek across Hawaiian Islands

(Update: 3:26 a.m. Oct. 27, 2026)

Chances for heavy showers will increase today as a trough passes over the island chain through Wednesday night. The trough will bring the threat of heavy flooding rainfall and thunderstorms before weakening Thursday or Friday, though humid conditions with a chance of heavy showers may linger, according to the National Weather Service.

Across the state this morning, clouds continue moving overhead from the southwest along with scattered showers. Winds on the Big Island summits have come down enough that the Wind Advisory was canceled. However, these winds are expected to increase later today and will likely support another Wind Advisory, according to the NWS.

NWS forecasters say remnants of Olana will remain far to the west and not directly impact the area. “A surface trough originating in the western Pacific extends through and several hundred miles east of the what remains of Olana. An upper level trough, well west of Kauaʻi will advance eastward, tapping moisture aloft from thunderstorms along the surface trough and sending increased high clouds overhead,” according to the NWS forecast.

Chances for heavy rainfall and thunderstorms will increase today as the upper level trough drifts closer to the state. Chances for widespread rain should remain relatively low in the morning as the Flood Watch for all islands goes into effect, but as moisture increases later in the day, the flood threat will slowly increase, the NWS reports.

The flood threat will be greatest this evening through Wednesday night. “The jet stream aloft will provide its strongest ascent over the region, pulling the surface trough over the state and possibly generating an elongated surface low near or over the islands. A deep tropical airmass will accompany this system and provide ample fuel for heavy rainfall,” according to the NWS forecast.

“Guidance shows the surface trough stretching across the central portion of the island chain, favoring Oʻahu and Maui County for the greatest rainfall totals. However, all islands will have a heavy rain threat, and slow- moving cells anchoring on terrain could drop very heavy rainfall in a short period of time, leading to flash flooding anywhere,” the NWS reports.

The threat of heavy rainfall will diminish Thursday and Friday. Friday night into Saturday a brief period of trade winds may return as the lingering moisture associated with the trough is pushed south of the islands. Breezy northeast winds are expected to develop Sunday as a shallow front moves near or over the state.