Hawaii Flash Flood Map: Hurricane Lane Prompts Warnings on Big Island, Maui

The National Weather Service's Honolulu office said Thursday that parts of the Big Island remained under a flash flood warning. Hawaii's Big Island was also under a hurricane warning as Hurricane Lane, a Category 4 storm, approached the island.

The flash flood warning is in effect for Hilo, Volcano and Honoka'a until 6:45 a.m. HST, the NWS said in an early morning tweet on Thursday. The warning urges residents to avoid walking or driving through flood waters and encourages people to immediately seek higher ground.

The NWS said that 121,467 residents are exposed to a potential flash flood. More than 30 schools and four hospitals are also included in the warning.

Hawaii was bracing itself for the Category 4 storm, which was already hitting the island with increasing rain on Wednesday. On Thursday, President Donald Trump signed a disaster declaration for the state, which has dealt with the destructive Kilauea volcano.

A hurricane warning noted that Lane may bring potential winds of 58 to 73 mph, although peak wind forecasts put wind speeds at 20 to 30 mph with gusts to 55 mph. The NWS warned that the wind impacts could be "significant" and said damage to homes, vehicles, trees, roads and power lines could occur.

Some areas could see up to two feet of storm surge through early Friday afternoon, the hurricane warning said. Rain amounts of 12 to 18 inches, with high localized amounts, are predicted. "Urgently consider protective actions from extreme and widespread rainfall flooding," the NWS wrote.

The warning also noted that the situation is "somewhat favorable" for tornadoes. Residents were urged to "be ready to shelter quickly" if a tornado warning was issued.

Shortly after reminding residents of the flash flood, the NWS issued a flood advisory for the island of Maui. "Radar indicated a large area of moderate to heavy rain moving across the windward and southeast slopes of Haleakala on East Maui, extending offshore across the Alenuihaha Channel to north of the Big Island," the advisory said.

The advisory added: "Stay away from streams, drainage ditches and low lying areas prone to flooding. Rainfall and runoff will also cause hazardous driving conditions due to ponding, reduced visibility and poor braking action."

The advisory, which is in place until 8 a.m. HST, includes Hana, Haliimaile, Pauwela, Kipahulu, Paia, Makawao, Keokea, Makena, Haiku-Pauwela, Wailea, Huelo, Ulupalakua and Kula.

Residents were urged not to cross fast flowing or rising water in their vehicles or on foot. "Turn around, don't drown," the NWS said.