Marine Weather and Tide Forecast for Hilo, HI

SHORT TERM UPDATE
Issued at 812 PM HST Sat Mar 21 2026

The forecast remains largely on track, with showers and isolated thunderstorms continuing over the smaller islands, moving eastward. Heaviest of showers are currently over Maui County, specifically around the Lanai which has seen 1 to 2 inches of precipitation in the last 6 hours as of 7:30 HST. Otherwise, isolated showers continue to develop southwest of the Hawaiian Islands. The Flood Watch remains in effect for Oahu, Maui County, and Big Island at this time as a result. Additionally, the Winter Storm Warning remains in effect through 6 PM Sunday for the Big Island summits. Outside of the showers, winds remain light across the region, therefore, no amendments were made to the forecast at this time.

PREV DISCUSSION
Issued at 335 PM HST Sat Mar 21 2026

Radar shows showers and isolated thunderstorms moving northeast over parts of the state. The largest area of showers as of 3 PM HST was over Maui County, with showers also over parts of the Big Island (mainly N and S Hilo).

The upper level trough that has brought us this kona storm continues to drift slowly east as it evolves, with shortwaves moving through the trough. Today, the associated surface low has started to move northeast away from the state. This is the beginning of the end of this system. However, it will remain close enough for a continued threat of flash flooding from Oahu east through the Big Island through Sunday afternoon. Flood warnings remain in effect this afternoon for much of Maui County. Periods of showers and isolated thunderstorms are still expected tonight and Sunday. Moisture levels remain high and cold temperatures aloft will bring continued instability. Therefore, rainfall rates have the potential to be high.

Sunday night and Monday, the upper trough will weaken and slowly slide across and east of the state. At the same time, the surface low will move significantly farther away. This will allow a high pressure center to build in to the north of the state, and trade winds will return Monday to the western islands, and Monday night to the eastern islands. Low level moisture left over from the kona storm will result in scattered windward showers on western and central islands Monday, with numerous showers on windward Big Island into Monday night. From Tuesday through the end of the week, expect typical trade wind weather, with isolated to scattered showers windward and very few if any showers on the leeward side.

AVIATION
Issued at 812 PM HST Sat Mar 21 2026

Bands of showers and embedded thunderstorms continue to move over Maui County and potentially may move east over the Big Island.
The ongoing kona low will support further rain bands, mainly across Oahu and Maui County, through the forecast period. Rainfall may spread to Kauai, though confidence is lower for the western end of the state. Winds will remain primarily out of the south to southwest. Expect widespread MVFR conditions over Maui County through the forecast period, with locally LIFR conditions under showers.

AIRMET Sierra is in effect for Molokai, Maui, and Lanai due to widespread low ceilings and showers and is expected to continue overnight. AIRMET Sierra is also in effect for Oahu due to mountain obscuration and will continue to monitor this through the night.

AIRMET Tango remains in effect for moderate turbulence downwind of terrain for Oahu and Maui County below 070 from gusty south to southwest winds associated with the kona low. However, winds are showing some signs of weakening, so we may be able to cancel this AIRMET later tonight or Sunday.

Light icing in layer 140-FL260 will also persist, mainly over the central portion of the state where the thick high clouds continue to stream over from the southwest.

MARINE
Issued at 335 PM HST Sat Mar 21 2026

Bands of heavy showers and a few thunderstorms will continue to move over portions of the coastal waters, especially the central and eastern waters, as a kona low continues to impact the state.
Prevailing southerly moderate to locally breezy winds continue across portions of the area as well. The low will lift farther north on Sunday, allowing light to moderate northerly winds to develop around Kauai, which will then veer to northeast and spread southward. Additionally, due to wave heights around Niihau, Kauai, and Oahu near 10 feet, a Small Craft Advisory remains in effect for those waters until 6AM Sunday.

A northerly swell is peaking today, and is producing borderline advisory-level surf for north facing shores of Niihau, Kauai, and Oahu as of this afternoon. This will continue into the evening hours before slowly declining overnight. As such, a High Surf Advisory (HSA) remains in effect for north facing shores for Niihau, Kauai, and Oahu until 6AM Sunday. Additionally, a slight bump is expected from a small, building west-northwest swell that will peak Sunday.

A small south swell is slowly declining and will continue to trend down through the rest of the weekend into early next week.
Smaller surf is expected along south facing shores through the remainder of the week. Surf along east-facing shores remains elevated due to wrap from the north swell, and will be near HSA thresholds. This swell will slowly diminish through the rest of the weekend as well.

HFO WATCHES/WARNINGS/ADVISORIES
High Surf Advisory until 6 AM HST Sunday for Kauai East-Kauai North-Koolau Windward-Niihau-Oahu North Shore-Olomana.

Flood Watch through Sunday afternoon for Big Island East-Big Island Interior-Big Island North-Big Island South-Big Island Southeast-Central Oahu-East Honolulu-Ewa Plain-Haleakala Summit- Honolulu Metro-Kahoolawe-Kipahulu-Kohala-Kona-Koolau Leeward- Koolau Windward-Lanai Leeward-Lanai Mauka-Lanai South-Lanai Windward-Maui Central Valley North-Maui Central Valley South- Maui Leeward West-Maui Windward West-Molokai Leeward South- Molokai North-Molokai Southeast-Molokai West-Molokai Windward- Oahu North Shore-Olomana-South Haleakala-South Maui/Upcountry- Waianae Coast-Waianae Mountains-Windward Haleakala.

Winter Storm Warning until 6 PM HST Sunday for Big Island Summits.

Small Craft Advisory until 6 AM HST Sunday for Kaiwi Channel- Kauai Channel-Kauai Leeward Waters-Kauai Northwest Waters-Kauai Windward Waters-Oahu Windward Waters.