Cyclone Daman is due to hit northern Vanua Levu island tonight and on over Taveuni and the islands of the Lau Group.
In the last two hours Cyclone Daman has changed course away from the tourist heavy areas of western Viti Levu.
Neighbouring Tonga has been put on alert.
"It has undergone some very erratic behaviour and its path is changing all the time," Fiji Meteorology Service head Rajendra Prasad told Fairfax Media a short time ago.
It was heading for the Vanua Levu town of Labasa which on January 14, 2003, was devastated by Cyclone Ami, killing nine people.
Daman is a now a category four hurricane on a five point scale and is stronger than Ami.
Prasad said while Vanua Levu is most likely to face the full force, he warned all of Fiji to be careful.
"This storm has been so unpredictable so far, if it could take a southward dive the rest of Fiji will get hit too."
Auckland engineer Murray Thomson is working on a resort on Laucala Island, just east of Taveuni and is in the bulls-eye.
He told Fairfax Media that they had suffered strong winds and heavy rains for the last couple of days but in the last couple of hours an "absolute calmness" has settled over the island.
Looking north, toward Daman, the sky was very black.
"But one thing you do note is that the water has taken on this beautiful pristine blue which is unusual with this kind of cloud cover," Thomson said.
People were moving around quickly getting ready with material tied down, containers re-packed and boats put out to sea.
There was no sense of panic.
"It seems to be calm with the people, they know what to do.... Its basically, the scenario, is the calm before the storm."
Dr Prasad said two days ago Daman was not taken seriously by international forecasting agencies which each day reach a consensus agreement on what will happen.
"At the beginning all these models were not giving it any interest, thinking it was a weak feeble thing."
But last night it underwent "explosive development" and grew in power and changed track several times.
In the latest formal warning the Fiji weather office says that at 11 am Daman was 235 kilometres west-northwest of Labasa and moving at 20 kilometres per hour.
They warn it may change course in the afternoon and are expecting it to cross Vanua Levu and out over Taveuni and the Northern Lau Group.
On the scale Daman "is a very severe cyclone and increasingly very dangerous".
Storm surges of three to five metres above normal are expected along the coast and flooding in low lying areas.
The weather office has called for evacuations.
"Resident and authorities in Tonga should closely watch this system as it works its way through the Lau Group."
A short time ago Air Pacific cancelled flights out of Nadi. In a statement they said flights to Auckland, Brisbane and Sydney were halted until operating conditions could be confirmed.
Sala Toganivalu of the Fiji Tourist Bureau said it was very calm in Nadi right now, with no strong winds and no rain.
"The calm before the storm I would think," he said.
State owned Fiji Broadcasting is reporting that Labasa was at a standstill with people racing to prepare for the storm.
Fiji's National Centre for Disaster Management says its offices nationwide are on full alert.
- Fairfax Media