People in Fiji's second largest town, Nadi, have been advised to get out after the Nadi River reached critical levels around lunchtime.
Evacuation centres have been opened and schools closed as a flood warning remains in force for low lying areas near Nadi River and downstream of Votualevu.
The head of the Nadi Basin Catchment Committee, Bryan Watson, says Nadi is preparing for serious floods equal to those in 2009 and 2012.
"The tide is still out but by five this afternoon we're expecting still increased rainfall and there's still rain in the hills so we expect flooding to take place at about five thirty when the tide again returns to a full 1.8m height and this will cause the backing up of the floodwaters."
Mr Watson says Nadi's shopkeepers and businesses have been taking precautions since flood warnings were issued early this morning.
The Fiji Meteorological Service has warned of heavy rain and flash flooding for the whole Fiji group as an active trough of low pressure remains over the islands and another trough moves towards the group.