Lala strengthened into a Category 1 hurricane on Aug 15, generating winds of up to 120kmh.

It “appears to have peaked in intensity” when it passed near South Point of the Big Island in the afternoon, and did not make landfall.

“The hurricane could maintain its intensity for a few more hours, but weakening is expected by early Sunday as Lala continues to pull away from the Big Island,” NHC officials said.

Aside from the Big Island, a tropical storm warning was in place for the state’s seven other major islands: Maui, Molokai, Kahoolawe, Lanai, Oahu, Kauai and Niihau.

A maximum storm total of 76cm to 89cm of rainfall was expected over the windward Big Island.

“Heavy rainfall, with life-threatening flooding and mudslides, especially in areas of steep terrain, will continue tonight into early Sunday over the Big Island and Maui,” officials warned.

The heavy rain and flood risk will then spread westward across the island chain on Aug 16, according to the NHC.

Power outages were reported for more than 20,000 customers in Hawaii on the afternoon of Aug 15, with weather officials confirming “damaging winds and heavy rain” were spreading across the Big Island famed for surfing and tourism.

Swells generated by Lala would build through the weekend and are likely to cause “life-threatening surf and rip current conditions”.

“It’s a serious storm,” Governor Josh Green said, proclaiming a state of emergency to ensure Hawaii and its counties “have sufficient resources to clear debris, secure infrastructure, and take other measures to prepare.”

Honolulu Mayor Rick Blangiardi said on Aug 14 his administration had spent days preparing for the storm, and urged residents to be ready.

The state was last hit by a “major” hurricane – meaning Category 3, 4, or 5 on the Saffir-Simpson scale – in 1992, when Hurricane Iniki caused at least six deaths and billions of dollars in damage.

Hawaii was menaced by Hurricane Fausto in July, before the storm weakened and skirted north of the island chain.

The storm comes as a powerful El Nino has formed in the central equatorial Pacific Ocean.

Temperatures are already so high that the National Oceanic and Atmosphere Administration now predicts a 69 per cent chance of a “historic event that would exceed the strength of previous El Nino events dating back to 1950” when it peaks between October and December.

El Nino, a natural climate pattern when sea surface temperatures in the central and eastern Pacific Ocean become unusually warm, tends to promote hurricane activity in the Pacific while suppressing it in the Atlantic.

Human-caused climate change can amplify El Nino’s impacts because a warmer ocean and atmosphere increase the availability of energy and moisture for extreme weather events, such as heat waves and heavy rainfall.

Hawaii’s emergency management agency recommended residents clear gutters and drains and move valuables off the ground, seal gaps in doors and remove tree limbs that threaten their properties. AFP