Kona Low Threatens Heavy Rain and Flooding on Big Island

National Weather Service forecasters and local meteorologists are tracking a kona low that will develop north of Kauai Saturday night and pass northwest then west of the island Sunday through Monday. The system will turn winds southerly and increase moisture across the state, producing the threat of heavy rainfall and thunderstorms statewide. The NWS posted a Flood Watch in effect from late Saturday night through Monday afternoon for all Hawaiian Islands. Hawaii News Now’s First Alert Weather Team has declared Sunday and Monday as FIRST ALERT WEATHER DAYS.

The greatest rainfall totals are expected over windward and southeast parts of Hawaii Island, where shower bands could stall and produce prolonged downpours. Meteorologists caution that stalled bands raise the risk of localized flash flooding on low-lying roads, valley streams, and developed coastal plains. Small craft advisories are in effect for various coastal waters as southeast winds increase, and a Coastal Flood Statement warns of possible minor coastal flooding during peak monthly high tides, particularly along north-facing shores as an incoming north swell arrives.

Breezy to possibly strong southeast winds are expected by Monday, which will exacerbate runoff and could down trees and utility lines in vulnerable areas. Forecasters also note the potential for snow or freezing rain on the island’s highest summits if elevation and temperatures support it, a consideration for summit access and operations.

Local impacts could be significant even if the system falls short of a major storm. Short-term economic effects include interrupted harbor activity and reduced small-boat fishing during advisories, delays or cancellations in coastal tourism and outdoor services, and increased costs for road clearing and debris removal. Agricultural operations on windward slopes may see saturated soils and crop stress where runoff concentrates; repeated intense rains strain insurance pools and local repair budgets. In the months and years ahead, emergency managers and county planners face pressure to prioritize drainage upgrades and shoreline resilience as extreme short-duration rainfall becomes a recurring budgetary stressor.

Residents should monitor updates closely, limit travel during heavy downpours, secure loose outdoor items, and avoid driving through flooded roadways. Use the First Alert Weather app and interactive radar for real-time watches and warnings. Stay alert to official guidance from county emergency management as the kona low moves through Sunday and Monday.