Hawaii's Kauai island receives flash flood warning as downpours continue after tropical storm Lane

Storm brought state's heaviest downpours in 68 years

A woman pushes her bike through flooding caused by tropical storm Lane in Hilo, on Hawaii's Big Island (REUTERS)

A flash flood warning has been issued for parts of Hawaii after tropical storm Lane drenched the state with more than 1.3 metres of rain.

The US National Weather Service (NWS) said a “trailing band of deep tropical moisture” would keep conditions wet in the wake of the storm, which caused major damage and forced the rescue of dozens of people on Sunday.

Lane’s downpours dumped more rain on the state than any storm in the past 68 years, according to preliminary figures.

A flash flood warning, meaning flooding is imminent, is in place until 8.45pm Tuesday local time (5.45am Wednesday BST) in Kauai, the northernmost of Hawaii’s main islands.

Some bus services have been restricted, parts of key roads have been shut and a primary school has been closed.

The rest of the state's islands have been placed under flash flood watch, a lesser alert which means flooding is possible.

The NWS said further rainfall in already saturated grounds could quickly lead to flooding.

It had been feared that Lane could cause devastation to Hawaii as it barrelled towards the islands as a category 5 hurricane last week.

Residents and businesses across the islands prepared for the worst, boarding up windows and stocking up on supplies.

In the event, the storm's winds slowed down drastically, although it still caused some damage. Forty people were rescued from their homes on Big Island, which bore the brunt of the storm.

Lane was downgraded to a tropical storm on Friday and all warnings for Hawaii were cancelled on Saturday morning after the storm turned west and moved away from the state.

But the slow-moving storm's outer bands dumped 51.53 inches (1.3 metres) of rain on Big Island, more than any storm since Hurricane Hiki in 1950.