"This is a once-in-a-lifetime rainfall situation,'' Prasad said.
He also said that in the town of Monasavu on Viti Levu island, more than 41 inches of rain had fallen in the past five days.
According to local officials, in the main tourism centre of Nadi, 38 inches have been recorded, flooding shops. Many likely will be forced out of business.
A state of emergency continues to be in force in western Viti Levu, where the tourism industry is based.
On Monday, the government declared a state of emergency in the hardest-hit western districts of Viti Levu.
Australia has announced it will give $101,000 towards flood relief efforts in Fiji, adding to $59,000 pledged by neighbouring New Zealand to the Fiji Red Cross.