SYDNEY - POPULAR tourist islands on Australia's Great Barrier Reef were bracing themselves on Saturday for wild weather, as a severe tropical cyclone closed in.

Cyclone Hamish was upgraded overnight to a category three storm system, with forecasters warning it could intensify to a category four hurricane in the next 24 hours.

On Saturday afternoon it was 250 kilometres east of tourist spot Cairns - a gateway to the Great Barrier Reef - and was bearing down on the Whitsundays island group.

'The system does seem to be running just parallel to the coast but the Whitsundays do stick out,' said Tony Auden, from the Cyclone Warning Centre.

'(With) the destructive wind gusts we could see anything up to 140, maybe 150 kilometres per hour tomorrow morning around the Whitsundays and perhaps even the central (Queensland) coast.' Officials on Hamilton Island, one of the largest islands in the group, said they were on cyclone warning blue.

'(That) means some of the residents (are) ready to move into the Reef View Hotel, which is our principal safe haven,' the island's chief executive Glen Bourke told the Australian Broadcasting Corporation.

The weather bureau said Hamish was unlikely to reach the Whitsundays until Sunday morning and would cross onto Australia's mainland in the late evening, or early Monday morning.

Australia's northeast was last devastated by a category four storm - the second-highest rating - in 2006, when Cyclone Larry caused damage amounting to an estimated A$500 million dollars (S$495 million) to crops and infrastructure. -- AFP